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| United States Patent |
5,554,686
|
|
Frisch, Jr.
, et al.
|
September 10, 1996
|
Room temperature curable silane-terminated polyurethane dispersions
Abstract
This invention provides aqueous dispersions of externally chain extended
polyurethane compositions terminated by hydrolyzable and/or hydrolyzed
silyl groups and containing anionic solubilizing or emulsifying groups,
particularly carboxyl groups. The invention also provides methods of
making both anionically and cationically stabilized polyurethane
dispersions. This invention further provides polyurethane dispersions
which are substantially organic solvent free (e.g. less than about 7
weight percent organic solvent) which cure to water and solvent resistant,
tough, scratch resistant, preferably light stable (non-yellowing)
polyurethane films. Such films are particularly useful as coatings for
wood substrates, including wood floorings, furniture, and marine surfaces.
| Inventors:
|
Frisch, Jr.; Kurt C. (Fridley, MN);
Edwards; Bruce H. (White Bear Lake, MN);
Sengupta; Ashok (London, CA);
Holland; Lowell W. (St.Paul Park, MN);
Hansen; Richard G. (St. Paul, MN);
Owen; Ian R. (River Falls, WI)
|
| Assignee:
|
Minnesota Mining and Manufacturing Company (Saint Paul, MN)
|
| Appl. No.:
|
557385 |
| Filed:
|
November 13, 1995 |
| Current U.S. Class: |
524/588; 524/591; 524/837; 524/838; 524/839; 524/840; 528/28 |
| Intern'l Class: |
C08L 083/08; C08L 075/12 |
| Field of Search: |
524/539,588,591,837,838,839,840
528/28
|
References Cited
U.S. Patent Documents
| 3179713 | Apr., 1965 | Brown | 330/186.
|
| 3627722 | Dec., 1971 | Selter | 524/869.
|
| 3632557 | Jan., 1972 | Brode, et al. | 260/77.
|
| 3640924 | Feb., 1972 | Hermann et al. | 260/13.
|
| 3814716 | Jun., 1974 | Kowalski et al. | 260/29.
|
| 3941733 | Mar., 1976 | Chang | 260/824.
|
| 4567228 | Jan., 1986 | Gaa et al. | 524/588.
|
| 4582873 | Apr., 1986 | Gaa et al. | 524/391.
|
| 4598131 | Jul., 1986 | Prucnal | 525/440.
|
| 4628076 | Dec., 1986 | Chang et al. | 525/440.
|
| 5041494 | Aug., 1991 | Franke et al. | 524/588.
|
| 5047294 | Sep., 1991 | Schwab et al. | 428/432.
|
| 5225267 | Jul., 1993 | Ochi et al. | 428/214.
|
| 5354808 | Oct., 1994 | Onwumere et al. | 524/837.
|
| Foreign Patent Documents |
| 0163214B1 | Aug., 1991 | EP | .
|
| 0315006B1 | Dec., 1992 | EP | .
|
| 933321 | May., 1993 | ZA.
| |
| WO90/10026 | Jul., 1990 | WO | .
|
Other References
Polyurethanes: Chemistry and Technology, Saunders and Frisch, Interscience
Publishers (New York, 1963 (Part I) and 1964 (Part II).
|
Primary Examiner: Szekely; Peter A.
Attorney, Agent or Firm: Griswold; Gary L., Kirn; Walter N., Dowdall; Janice L.
Parent Case Text
This is a continuation of application Ser. No. 08/109,640 filed Aug. 20,
1993, now abandoned.
Claims
We claim:
1. An anionically stabilized polymer composition comprising polymer of
formula (I)
[SIL--X]--ISO--Y--[POL--X--ISO--Y].sub.n .about.[CE--X--ISO--Y].sub.m
.about.[WSC--X--ISO--Y].sub.q --[SIL] (I)
wherein [POL--X--ISO--Y], [CE--X--ISO--Y], and [WSC--X--ISO--Y] can be
randomly distributed or form blocks;
wherein
SIL represents
##STR12##
R.sup.3 is selected from the group consisting of hydrogen; alkyl radicals
comprising about 1 to about 4 carbon atoms; acyl groups comprising about 2
to about 5 carbon atoms; and oxime groups of the formula --N.dbd.CR.sup.5
R.sup.6, wherein R.sup.5 is a monovalent alkyl group comprising about 1 to
about 12 carbon atoms and wherein R.sup.6 is a monovalent alkyl group
comprising about 1 to about 12 carbon atoms;
R.sup.4 is a divalent radical comprising about 2 to about 20 carbon atoms,
wherein said radical contains no isocyanate reactive functional groups;
p represents an integer of 1 to 3;
X is a divalent radical selected from the group consisting of
##STR13##
wherein R is independently selected from the group consisting of phenyl,
linear aliphatic groups comprising about 1 to about 12 carbon atoms,
branched aliphatic groups comprising about 1 to about 12 carbon atoms, and
cycloaliphatic groups;
ISO represents a moiety derived from a polyisocyanate component comprising
a compound having 2 isocyanate groups and optionally further comprising a
compound having greater than 2 isocyanate groups;
Y is a divalent radical selected from the group consisting of
##STR14##
wherein R is as defined above; POL represents a moiety derived from a
polyol component comprising a compound having 2 isocyanate reactive
functional groups and optionally a compound having greater than 2
isocyanate reactive functional groups, each isocyanate reactive functional
group having at least one active hydrogen;
n represents an integer of about 2 to about 85;
CE represents a moiety derived from a chain extender component comprising a
difunctional chain extender having 2 isocyanate reactive functional groups
and optionally a polyfunctional chain extender having at least 3
isocyanate reactive functional groups each isocyanate reactive functional
group having at least one active hydrogen, wherein the chain extender
component specifically excludes difunctional sterically hindered amines
having the general formula
##STR15##
wherein: R.sup.7, R.sup.8 R.sup.9 are independently selected from the
group consisting of cyclic and aliphatic organic radicals free of
isocyanate reactive functional groups, and with the proviso that at least
75% of the R.sup.9 groups have at least 4 carbon atoms;
m represents an integer of about 1 to about 84;
WSC represents a moiety derived from a water-solubilizing compound, wherein
the water solubilizing compound possesses at least one water solubilizing
group and at least two isocyanate reactive functional groups, each
isocyanate reactive functional group containing at least one active
hydrogen wherein the water solubilizing group is reacted with a basic salt
forming compound to anionically stabilize the polymer;
q represents an integer of about 2 to about 85;
wherein the urethane branching coefficient of the polymer is about 1.7 to
about 2.25; and wherein sufficient polyisocyanate component is included to
provide an excess on an isocyanate equivalent basis of about 1.4 to about
4 times the combined active hydrogen equivalent of the isocyanate reactive
functional groups of the polyol component, the water solubilizing
compound, and the chain extender component.
2. The composition of claim 1 wherein n represents an integer of about 3 to
about 65; m represents an integer of about 2 to about 64, and q represents
an integer of about 3 to about 65.
3. The composition of claim 1 wherein n represents an integer of about 4 to
about 15; m represents an integer of about 2 to about 64; and q represents
an integer of about 4 to about 15.
4. The composition of claim 1 wherein R.sup.3 is selected from the group
consisting of ethyl and methyl; and p is 3; and R.sup.4 comprises 2 to 4
carbon atoms.
5. The composition of claim 1 wherein said polyol is selected from the
group consisting of poly(oxypropylene) glycols, ethylene oxide capped
poly(oxypropylene) glycols, poly(oxytetramethylene) glycols,
.alpha.-omega-diamino poly(oxypropylene), aromatic amine-terminated
poly(oxypropylene) glycols, graft-polyether polyols, poly(oxyethylene)
polyols, polyglycol adipates, polyethylene terephthalate polyols,
polycaprolactone polyols, polybutadiene polyols, hydrogenated
polybutadiene polyols, .alpha.-omega-diamino poly(oxytetramethylene),
polythioether polyols, polybutylene oxide polyols,
polyoxytetramethylene/ethylene oxide random copolymer polyols, fluorinated
polyether polyols, acrylic polyols, polycarbonate polyols, and mixtures
thereof.
6. The composition of claim 1 wherein said polyol component has a number
average molecular weight of about 250 to about 35,000.
7. The composition of claim 1 wherein said polyol component has a number
average molecular weight of about 500 to about 3000.
8. The composition of claim 1 wherein said water solubilizing compound is
selected from the group consisting of
[H.sub.2 N(CH.sub.2).sub.n CH.sub.2 ].sub.2 NCH.sub.3 wherein n is an
integer of 1 to 3;
(HOCH.sub.2 ).sub.2 C(CH.sub.3)COOH;
[HO(CH.sub.2).sub.n CH.sub.2 ].sub.2 NCH.sub.3 wherein n is an integer of 1
to 3;
H.sub.2 N--C.sub.2 H.sub.4 --NH--C.sub.2 H.sub.4 --SO.sub.3 H;
H.sub.2 N--C.sub.3 H.sub.6 --N(CH.sub.3)--C.sub.3 H.sub.6 --SO.sub.3 H;
##STR16##
HOCH.sub.2 --CH(OH)--CO.sub.2 Na; [(HOCH.sub.2).sub.2 CHCH.sub.2
--COO].sup.- [NH(CH.sub.3).sub.3 ].sup.+ ;
##STR17##
CH.sub.3 (CH.sub.2).sub.2 CH(OH)--CH(OH)(CH.sub.2).sub.3 CO.sub.2 K;
(HOC.sub.2 H.sub.4).sub.2 N--C.sub.3 H.sub.6 --OSO.sub.3 Na;
[H.sub.2 N--C.sub.2 H.sub.4 --NH--C.sub.2 H.sub.4 --N(CH.sub.3).sub.3
].sup.+ Cl.sup.- ;
##STR18##
(HOCH.sub.2 CH.sub.2).sub.2 NC.sub.6 H.sub.4 O(CH.sub.2 CH.sub.2
O)SO.sub.2 OH;
[(H.sub.2 N).sub.2 C.sub.6 H.sub.3 SO.sub.3 ].sup.- [NH(C.sub.2
H.sub.5).sub.3 ].sup.+, and mixtures thereof.
9. The composition of claim 1 wherein said basic salt forming compound is
selected from the group consisting of ammonia, trimethylamine,
triethylamine, tripropylamine, triisopropylamine, tributylamine,
triethanolamine, diethanolamine; and mixtures thereof.
10. The composition of claim 1 wherein said difunctional chain extender is
selected from the group consisting of 1,4-butanediol, ethylene glycol,
diethylene glycol, dipropylene glycol, neopentyl glycol, 1,6-hexanediol,
1,4-cyclohexane dimethanol, bis(2-hydroxylethyl) hydroquinone,
4,4'-methylene bis(o-chloroaniline), 2,5-diethyl-2,4-toluene diamine,
4,4'-methylene bis(3-chloro-2,6-diethylaniline), propylene glycol
bis(4,4'-aminobenzoate), 3,5-di(thiomethyl)-2,4-toluene diamine, methylene
bis(4,4'-aniline), ethyl-1,2-di(2-amino thiophenol), 4-chloro-3,5-diamino
isobutylbenzoate, 1,2-diaminoethane, N,N'-dialkyl(methylene dianiline),
N,N'-dialkyl(1,4-diaminobenzene), and mixtures thereof.
11. The composition of claim 1 wherein the isocyanate reactive silane is
selected from the group consisting of
H.sub.2 NCH.sub.2 CH.sub.2 CH.sub.2 Si(OC.sub.2 H.sub.5).sub.3 ;
H.sub.2 NCH.sub.2 CH.sub.2 CH.sub.2 Si(OCH.sub.3).sub.3 ;
##STR19##
HSCH.sub.2 CH.sub.2 CH.sub.2 Si(OCH.sub.3).sub.3 ; HO(C.sub.2 H.sub.4
O).sub.3 C.sub.2 H.sub.4 N(CH.sub.3)(CH.sub.2).sub.3 Si(OC.sub.4
H.sub.9).sub.3 ;
H.sub.2 NCH.sub.2 C.sub.6 H.sub.4 CH.sub.2 CH.sub.2 Si(OCH.sub.3).sub.3 ;
HSCH.sub.2 CH.sub.2 CH.sub.2 Si(OCOCH.sub.3).sub.3 ;
HN(CH.sub.3)CH.sub.2 CH.sub.2 Si(OCH.sub.3).sub.3 ;
HSCH.sub.2 CH.sub.2 CH.sub.2 SiCH.sub.3 (OCH.sub.3).sub.2 ;
(H.sub.3 CO).sub.3 SiCH.sub.2 CH.sub.2 CH.sub.2 NHCH.sub.2 CH.sub.2
CH.sub.2 Si(OCH.sub.3).sub.3 ; and mixtures thereof.
12. The composition of claim 1 wherein the urethane branching coefficient
represents a numeral of about 1.85 to about 2.01.
13. A film comprising the cured composition of claim 1.
14. An elastomer comprising the cured composition of claim 1.
15. The cured composition of claim 1.
16. A composition comprising:
(a) about 85 to about 99.9 percent by weight of the dispersion of claim 1;
(b) about 0.1 to about 10 percent by weight of a photostabilizer;
(c) about 0 to about 10 percent by weight of a surfactant; and
(d) about 0 to about 10 percent by weight of a thickening agent;
wherein the weight percentages are based upon the total weight of the
coating composition and total 100%.
17. The cured composition of claim 16.
Description
FIELD OF THE INVENTION
This invention relates to aqueous dispersions of externally chain extended
polyurethane compositions terminated by hydrolyzable and/or hydrolyzed
silyl groups and containing anionic solubilizing or emulsifying groups,
particularly carboxyl groups. The invention also relates to methods of
making both anionically and cationically stabilized polyurethane
dispersions. This invention further relates to polyurethane dispersions
which are substantially organic solvent free (e.g. less than about 7
weight percent organic solvent) which cure to water and solvent resistant,
tough, scratch resistant, preferably light stable (non-yellowing)
polyurethane films and which can be formulated to achieve high gloss. Such
films are particularly useful as coatings for wood substrates, including
wood floorings, furniture, and marine surfaces.
BACKGROUND OF THE INVENTION
It is well known to treat substrates such as wood with polyurethanes or
alkyd resins. Polymers are: generally applied either neat or from solvent
solution as one-part or two-part systems. Frequently, isocyanate
terminated polymers are used. The toxicological problems associated with
free monomeric isocyanates are well known. It is desirable to make a
coating where the end user is not exposed to free monomeric isocyanates.
In addition, the use of solvents creates problems of pollution, toxicity,
and flammability and increases the cost of formulating and processing
polyurethane materials. Solvents, however, are often required in the
preparation and handling of polyurethane resins to sustain a controllable
and processible viscosity.
Many of the known references emphasize polyurethane materials which are
unstable to water and are generally kept from contact with water until
after application to the surface being treated, e.g., leather. Thus, U.S.
Pat. No. 3,179,713 (Brown) describes the surface treatment of leather with
polysiloxanes containing isocyanate radicals as terminal groups. These are
employed in amounts of 10-75 % by weight with triorganosilyl endblocked
diorganopolysiloxanes. The resulting product has all the characteristics
of a siloxane-treated leather, except that the reactive isocyanate groups
are stated to provide better bonding. Such compositions must be applied
from solvent and must be protected from exposure to moisture prior to
application to the leather. The compositions are applied at 15 % to 25 %
by weight of the leather.
A class of moisture-curable silyl group-containing polymers is described by
Brode et al., U.S. Pat. No. 3,632,557. The polymers are described as
"vulcanizable" and are formed as films and plaques which cure by exposure
to atmospheric moisture. Because of this sensitivity, the patentee taught
that care had to be exerted at all times to avoid premature exposure to
moisture. A polyurethane sealant containing; alkoxysilyl terminating
groups is described by Seiter, U.S. Pat. No. 3,627,722.
Latex polymers which are vinyl addition polymers formed by free radical
polymerization and comprise vinyl hydrolyzable silane, an ester of the
group of acrylic, maleic and fumaric esters and/or vinyl acetate are
described by Kowalski et al. in U.S. Pat. No. 3,814,716. These are
dispersed in water using anionic or nonionic surfactants and are said to
be useful to give durable coatings on various substrates which are
generally rigid. It is known that the introduction of surfactants to such
systems enhances the hydrophilicity of latices stabilized in this manner,
leading to a reduced moisture resistance and surface adhesion of such
coatings.
Gaa et al., U.S. Pat. No. 4,582,873 describes a process for making an
aqueous dispersible, polyurethane: polymer which has internal pendant,
siliconate anions. The aqueous dispersion is prepared from a reaction
product of polyisocyanates, organic compounds with at least 2 active
hydrogens, a hydrophilic additive, and organosilane which is at least
monofunctional, preferably difunctional, in reaction with isocyanate
groups on at least one organic moiety of the organosilane and also has at
least one hydrolyzed or hydrolyzable groups associated with the silicone
atom. The hydrophilic additive, which is present at a level of up to about
10 weight percent of the prepolymer or polymer depending on the
hydrophilicity of the polyisocyanates employed, assists in promoting the
emulsification and stability of the disclosed aqueous dispersions. The
aqueous dispersion of the polyurethane resin is used in coating a variety
of substrates such as inorganic oxide substrates.
Gaa, European Patent Appl. 0305833 B1, discloses a silane terminated
hydrophilic material based on vinyl alcohol and copolymers thereof as well
as sugars, which may be a solution or dispersion.
U.S. Pat. No. 5,041,494 (Franke et al.) discloses a cationically stabilized
silane terminated polyurethane made with hydrophilic polyether compounds
and, optionally, externally added alcoholic, aminic and/or hydrazinic
chain lengthening agents. These polyurethanes are made via a volatile
organic solvent process, wherein the volatile organic solvent is
introduced early in the polyurethane prepolymer formation and which must
be stripped from the final product via an additional step.
One means for reducing the moisture sensitivity that arises due to the
addition of these dispersant stabilizers in polyurethane dispersions, such
as nonionic, cationic, and anionic surfactants and other hydrophilic
additives, is through the use of external crosslinkers. Such external
crosslinking agents, added to improve hydrophobicity of the coatings
stabilized using these hydrophilic additives, can lead to other handling
and processing problems, including limited potlife and potential toxicity
problems associated with some of the commonly employed crosslinking
agents.
U.S. Pat. No. 3,941,733 (Chang) describes dispersions of polyurethane
containing pendant water-solubilizing groups and terminated by
hydrolyzable or hydrolyzed silyl groups which can form self-supporting
films and coatings on webs. Such water-solubilizing groups are introduced
to the polyurethane through the reaction of a stoichiometric excess of an
isocyanate-terminated prepolymer with a water-solubilizing compound which,
in addition to the water-solubilizing group, has two isocyanate-reactive
hydrogen atoms. To form higher molecular weight poly(urethane-ureas),
Chang internally chain extends with the water to form multiplicities of
chain extending urea linkages rather than incorporating externally added
chain extenders. Leather coated with one of these compositions has
excellent wear-resistance.
The inclusion of water-solubilizing compounds, such as diol acids, in
conjunction with salt-forming compounds, such as tertiary amines, in
polyurethane compositions has been described by Herman et al., in U.S.
Pat. No. 3,640,924. The intermediates are emulsified in the presence of
salt-forming compounds and thickeners are added to give curable adhesives.
Polyurethanes have also achieved commercial acceptance in wood finishing
systems because of their overall balance of properties, such as abrasion
resistance, flexibility, toughness, high gloss, as well as mar and solvent
resistance. Early commercial systems were either solvent based reactive
high solids prepolymers reacted with a second component, solvent-based
moisture curing compositions, or fully reacted urethane lacquers generally
dissolved in alcohols and/or aromatic solvents.
In an effort to eliminate solvents and their associated emission and
handling problems, waterborne urethane wood coatings were developed. One
means established for approaching the performance of solventborne
polyurethanes in a waterborne composition has been to add an external
crosslinker to the polyurethane dispersions. While these additives do
improve the durability of such two-part coatings, crosslinked compositions
unfortunately also present problems of limited pot life and potential
toxicity due to the chemical nature of many of the standard external
crosslinkers (e.g., multifunctional isocyanate and aziridine crosslinking
agents).
The primary function of cleat wood finishes is to enhance the natural
beauty and protect wood surfaces from cumulative weathering effect of
sunlight and moisture. Silicone containing finishes are preferred for use
in harsh marine applications to protect wood above the water line from
exposure to sun, rain, and salt-fog. However, the adhesion of silicones to
oil woods, like teak, is poor. For teak, known polyurethane coatings
adhere well but experience degradation upon exposure to sunlight. Wood
continually undergoes dimensional changes caused by fluctuations in
humidity and temperature in the use environment. The rate and magnitude of
these changes can be controlled to some degree by the moisture
permeability of the coating. Therefore, a wood coating must have
sufficient elasticity to expand and contract with the wood, yet have
adequate adhesion to resist the interfacial stress generated by the
differential movement between the coating and wood surface. Coatings
having a low modulus of elasticity will generate less interfacial stress
for a given amount of movement than those with a high modulus. Hydrophilic
coatings are plasticized by adsorbed water which increases their
elasticity and peel tendency.
The weathering of wood proceeds by a series of complex, free-radical
chemical reactions. The free radicals are photolytically generated in wood
by both ultraviolet (UV) and visible light. Small amounts of moisture (0
to 6% ) increase the concentration of free-radicals. These radicals
rapidly react with atmospheric oxygen to oxidize (degrade) the wood
surface. While UV light stabilized, clear wood finish coatings can slow
the ingress of moisture and light and thus retard the degradation process
to some degree, eventually the wood at the interface deteriorates causing
the coating to flake and chip-off the surface. The rate of these
degradation reactions is a function of the finish film composition and
moisture adsorption/permeation.
SUMMARY OF THE INVENTION
It would be desirable to have the advantages of silicon-containing groups,
particularly curability, in a polyurethane composition which is not
sensitive to water. A need thus exists for a stable, curable composition
containing polyurethane and silyl groups which is not sensitive to
moisture before application and which reduces the content of expensive and
polluting solvents for application. A need also exists for silyl
group-containing polyurethanes which are film-forming. A need also exists
for a method of producing low viscosity polyurethane dispersions which are
stable to shear as to be mechanically pumpable. A need also exists for
substantially organic solvent free water and solvent resistant, scratch
resistant, and non-yellowing polyurethane films.
We have discovered that hydrolyzable and/or hydrolyzed silyl-terminated
polyurethanes in aqueous dispersion which have excellent stability and
which are useful as film-forming and coating materials. The term
polyurethane, or sometimes polyurethane-polyurea, refers to a polymeric
material, the backbone of which comprises a multiplicity of urethane
linkages,
##STR1##
and may also contain one or more urea linkages:
##STR2##
and may also contain one or more thiocarbamate linkages:
##STR3##
and combinations thereof.
Aqueous polyurethane dispersions of the invention are found to be stable to
shear, to have enhanced chemical and mechanical stability, and to have
relatively low viscosities even at high polymer concentrations. They
present reduced hazards and costs as compared to known polyurethane
solutions because of their lower solvent contents. Because they are
aqueous, there are no problems associated with continuous maintenance of
anhydrous conditions prior to use. Films formed from these dispersions are
free from the problems associated with the presence of surfactants which
are encountered with films formed from conventional externally emulsified
dispersions. External crosslinking agents (the toxicity problems of which
were discussed in the Background of the Invention), may be used, but are
not required.
The anionically stabilized polymer composition of the invention comprises
polymer of the formula (I)
[SIL--X]--ISO--Y--[POL--X13 ISO--Y].sub.n .about.[CE--X--ISO--Y].sub.m
.about.[WSC--X--ISO--Y].sub.q --[SIL] (I)
wherein [POL--X--ISO--Y], [CE--X--ISO--Y] and [WSC--X--ISO--Y] can be
randomly distributed or form blocks;
wherein
SIL represents
##STR4##
R.sup.3 is selected from the group consisting of hydrogen, alkyl radicals
comprising about 1 to about 4 carbon atoms; acyl groups comprising about 2
to about 5 carbon atoms; and oxime groups of the formula --N.dbd.CR.sup.5
R.sup.6, wherein R.sup.5 is a monovalent alkyl group comprising about 1 to
about 12 carbon atoms and wherein R.sup.6 is a monovalent alkyl group
comprising about 1 to about 12 carbon atoms;
R.sup.4 is a divalent radical comprising about 2 to about 20 carbon atoms,
wherein said radical contains no isocyanate reactive functional groups;
p represents an integer of 1 to 3;
X is a divalent radical selected from the group consisting of
##STR5##
wherein R is independently selected from the group consisting of phenyl,
linear aliphatic groups comprising about 1 to about 12 carbon atoms,
branched aliphatic groups comprising about 1 to about 12 carbon atoms, and
cycloaliphatic groups;
ISO represents a moiety derived from a polyisocyanate component comprising
a compound having 2 isocyanate groups and optionally further comprising a
compound having greater than 2 isocyanate groups;
Y is a divalent radical selected from the group consisting of
##STR6##
wherein R is as defined above;
POL represents a moiety derived from a polyol component comprising a
compound having 2 isocyanate reactive functional groups and optionally a
compound having greater than 2 isocyanate reactive functional groups, each
isocyanate reactive functional group having at least one active hydrogen;
n represents an integer of about 2 to about 85;
CE represents a moiety derived from a chain extender component comprising a
difunctional chain extender having 2 isocyanate reactive functional groups
and optionally a polyfunctional chain extender having at least 3
isocyanate reactive functional groups each isocyanate reactive functional
group having at least one active hydrogen;
m represents an integer of about 1 to about 84;
WSC represents a moiety derived from a water-solubilizing compound, wherein
the water solubilizing compound possesses at least one water solubilizing
group and at least two isocyanate reactive functional group, each
isocyanate reactive functional group containing at least one active
hydrogen wherein the water solubilizing group is reacted with a basic salt
forming compound to anionically stabilize the polymer;
q represents an integer of about 2 to about 85;
wherein the urethane branching coefficient of the polymer is about 1.7 to
about 2.25; and wherein sufficient polyisocyanate component is included to
provide an excess on an isocyanate equivalent basis of about 1.4 to about
4 times the combined active hydrogen equivalent of the isocyanate reactive
functional groups of the polyol component, the water solubilizing
compound, and the chain extender component.
The symbol ".about." represents a chemical bond and indicates that the
monomer units can be randomly distributed or form blocks.
The invention also relates to protective coatings for wood substrates
prepared from the polyurethane dispersions of the present invention. Such
wood coatings, particularly for wood furniture, floorings, and marine
surfaces, possess superior shelf stability, strain resistance, solvent
resistance, durability, toughness over the one-part and two-part
waterborne polyurethane coatings currently available. The wood coatings of
the present invention also possess unlimited pot-life and are free from
the potential toxicity hazard encountered with polyurethane materials
which require external crosslinking agents.
The invention also relates to methods of making hydrolyzable and/or
hydrolyzed silyl-terminated polyurethanes in aqueous dispersions and the
polyurethanes made therefrom.
A first method of making a silyl-terminated polyurethane in an aqueous
dispersion comprises the steps of:
(a) reacting a mixture comprising:
(i) a polyol component comprising a compound having isocyanate reactive
functional groups and optionally a compound having greater than 2
isocyanate reactive functional groups, each isocyanate reactive functional
group having at least one active hydrogen;
(ii) a water-solubilizing compound, wherein the water solubilizing compound
possesses at least one: water solubilizing group and at least one
isocyanate reactive functional group, each isocyanate reactive functional
group containing at least one active hydrogen; and
(iii) a polyisocyanate component comprising a compound having 2 isocyanate
groups and optionally further comprising a compound having greater than 2
isocyanate groups; wherein sufficient polyisocyanate component is included
to provide an excess on an isocyanate equivalent basis of about 1.4 to
about 4 times the combined active hydrogen equivalent of the isocyanate
reactive functional groups of the polyol component and the
water-solubilizing compound;
(iv) optional polar organic coalescing solvent;
(v) optional catalyst;
at a sufficient temperature in order to facilitate reaction of the mixture
to form an isocyanate-terminated polyurethane prepolymer; wherein the
ratio of the isocyanate groups of the polyisocyanate component to the
water solubilizing groups of the water solubilizing compound is such that
the prepolymer can provide a stable dispersion upon combination with a
water phase;
(b) preparing a stable silyl-terminated polyurethane dispersion by
combining under sufficient agitation and at a sufficient temperature and
pH the isocyanate terminated polyurethane prepolymer prepared according to
the step of element (a) with a water phase comprising:
(i) deionized water;
(ii) a chain extender component comprising a difunctional chain extender
having 2 isocyanate reactive functional groups and optionally a
polyfunctional chain extender having at least 3 isocyanate reactive
functional groups, each isocyanate reactive functional group having at
least one active hydrogen;
(iii) an isocyanate reactive silane compound having at least one active
hydrogen; and
(iv) a salt forming compound selected from the group consisting of basic
salt forming compounds and acidic salt forming compounds, wherein the salt
forming compound is selected such that the salt forming compound is
reactive with the water solubilizing group(s) in the water solubilizing
compound; wherein some or all of the salt forming compound is
alternatively added to the mixture of step (a) prior to or during
reaction, or to the isocyanate terminated polyurethane prepolymer prior to
the combination of the isocyanate terminated polyurethane prepolymer with
the water phase;
wherein a sufficient amount of the chain extender component and the
isocyanate reactive silane is present relative to excess polyisocyanate
component such that the active hydrogen to isocyanate group ratio is about
0.85:1 to about 1:1; and wherein the optional polar organic coalescing
solvent of element (a) (iv) can optionally be added 1:o the water phase
prior to the formation of the dispersion.
A second method of making a hydrolyzable, silyl-terminated polyurethane in
an aqueous dispersion comprises the steps of:
(a) reacting a mixture comprising:
(i) a polyol component comprising a compound having 2 isocyanate reactive
functional groups and optionally a compound having greater than 2
isocyanate reactive functional groups, each isocyanate reactive functional
group having at least one active hydrogen;
(ii) a water-solubilizing compound, wherein the water solubilizing compound
possesses at least one water solubilizing group and at least one
isocyanate reactive functional group, each isocyanate reactive functional
group containing at least one active hydrogen;
(iii) a chain extender component comprising a difunctional chain extender
having 2 isocyanate reactive functional groups and optionally a
polyfunctional chain extender having at least 3 isocyanate reactive
functional groups, each isocyanate reactive functional group having at
least one active hydrogen;
(iv) a polyisocyanate component comprising a compound having 2 isocyanate
groups and optionally further comprising a compound having greater than 2
isocyanate groups; wherein sufficient polyisocyanate component is included
to provide an excess on an isocyanate equivalent basis of about 1.4 to
about 4 times the combined active hydrogen equivalent of the isocyanate
reactive functional groups of the polyol component the water solubilizing
compound, and the chain extender component;
(v) optional polar organic coalescing solvent; and
(vi) optional catalyst;
at a sufficient temperature in order to facilitate reaction of the mixture
of element (a) to form a chain extended isocyanate-terminated polyurethane
prepolymer; wherein the ratio of the isocyanate groups of the
polyisocyanate component to the water solubilizing group(s) of the water
solubilizing compound is such that the prepolymer can provide a stable
dispersion upon combination with a water phase;
(b) preparing a stable silyl-terminated polyurethane dispersion by
combining under sufficient agitation and at a sufficient temperature and
pH the chain extended isocyanate terminated polyurethane prepolymer of (a)
with a water phase comprising:
(i) deionized water;
(ii) an isocyanate reactive silane compound having at least one active
hydrogen; and
(iii) a salt forming compound selected from the group consisting of basic
salt forming compounds and acidic salt forming compounds wherein the salt
forming compound is selected such that the salt forming compound is
reactive with the water solubilizing group(s) in the water solubilizing
compound; wherein some or all of the salt forming compound is
alternatively added to the mixture of step (a) prior to or during
reaction, or to the isocyanate terminated polyurethane prepolymer prior to
the combination of the isocyanate terminated polyurethane prepolymer with
the water phase;
wherein a sufficient amount of the isocyanate reactive silane is present
relative to excess polyisocyanate component such that the active hydrogen
to isocyanate group ratio is about 0.85:1 to about 1:1; and wherein the
optional polar organic coalescing solvent of element (a)(v) can optionally
be added to the water phase prior to the formation of the dispersion.
A third method of making a hydrolyzable, silyl-terminated polyurethane in
an aqueous dispersion comprises the steps of:
(a) reacting a mixture comprising:
(i) a polyol component comprising a compound having 2 isocyanate reactive
functional groups and optionally a compound having greater than 2
isocyanate reactive functional groups, each isocyanate reactive functional
group having at least one active hydrogen;
(ii) a water-solubilizing compound, wherein the water solubilizing compound
possesses at least one water solubilizing group and at least one
isocyanate reactive functional group, each isocyanate reactive functional
group containing at least one active hydrogen;
(iii) a chain extender component comprising a difunctional chain extender
having 2 isocyanate reactive functional groups and optionally a
polyfunctional chain extender having at least 3 isocyanate reactive
functional groups, each isocyanate reactive functional group having at
least one active hydrogen; and
(iv) a polyisocyanate component comprising a compound having 2 isocyanate
groups and optionally further comprising a polyisocyanate having at least
3 isocyanate groups;
(v) optional polar organic coalescing solvent; and
(vi) optional catalyst;
at a sufficient temperature in order to facilitate reaction of the mixture
to form a chain extended isocyanate-terminated polyurethane prepolymer;
wherein the ratio of the isocyanate groups of the polyisocyanate component
to the water solubilizing groups of the water solubilizing component is
such that the prepolymer can provide a stable dispersion upon combination
with a water phase;
(b) when the reaction of the mixture of element (a) is about 80 to about
90% complete, adding to the mixture of element (a) a polyisocyanate adduct
having greater than 2 isocyanate groups to form a branched chain extended
isocyanate terminated polyurethane prepolymer; wherein sufficient
polyisocyanate component and polyisocyanate adduct is included to provide
an excess on an isocyanate equivalent basis of about 1.4 to about 4 times
the combined active hydrogen equivalent of the isocyanate reactive
functional groups of the polyol component, the water-solubilizing
compound, and the chain extender component;
(c) preparing a stable silyl-terminated polyurethane dispersion by
combining under sufficient agitation and at a sufficient temperature and
pH the branched chain-extended isocyanate-terminated polyurethane
prepolymer of (b) with a water phase comprising:
(i) deionized water;
(ii) an isocyanate reactive silane compound having at least one active
hydrogen;
(iii) a chain extender component comprising a difunctional chain extender
having 2 isocyanate reactive functional groups and optionally a
polyfunctional chain extender having at least 3 isocyanate reactive
functional groups, each isocyanate reactive functional group having at
least one active hydrogen; and
(iv) a salt forming compound selected from the group consisting of basic
salt forming compounds and acidic salt forming compounds, wherein the salt
forming compound is selected such that the salt forming compound is
reactive with the water solubilizing group(s) in the water solubilizing
compound wherein some or all of the salt forming compound is alternatively
added to the mixture of step (a) or the mixture of step (b) prior to
combination of the branched chain-extended isocyanate-terminated
polyurethane prepolymer with the water phase;
wherein a sufficient amount of the isocyanate reactive silane is present
relative to excess polyisocyanate such that the active hydrogen to
isocyanate group ratio is about 0.85:1 to about 1:1; wherein (a)(v) can
optionally be added to the water phase prior the formation of the
dispersion.
A fourth method of making a hydrolyzable, silyl-terminated polyurethanes in
an aqueous dispersion comprising the steps of:
(a) reacting a mixture comprising:
(i) a polyol component comprising a compound having 2 isocyanate reactive
functional groups and optionally a compound having greater than 2
isocyanate reactive functional groups, each isocyanate reactive functional
group having at least one active hydrogen;
(ii) a water-solubilizing compound, wherein the water solubilizing compound
possesses at least one water solubilizing group and at least one
isocyanate reactive functional group, each isocyanate reactive functional
group containing at least one active hydrogen;
(iii) a chain extender component comprising a difunctional chain extender
having 2 isocyanate reactive functional groups and optionally a
polyfunctional chain extender having at least 3 isocyanate reactive
functional groups, each isocyanate reactive functional group having at
least one active hydrogen;
(iv) a polyisocyanate component comprising a compound having 2 isocyanate
groups and optionally further comprising a compound having greater than 2
isocyanate groups wherein sufficient polyisocyanate component is included
to provide an excess on an isocyanate equivalent basis of about 1.4 to
about 4 times the combined active hydrogen equivalent of the isocyanate
reactive functional groups of the polyol component, the water solubilizing
compound, and the chain extender component;
(v) optional polar organic coalescing solvent; and
(vi) optional catalyst;
at a sufficient temperature in order to facilitate reaction of the mixture
to form a chain-extended isocyanate-terminated polyurethane prepolymer,
(b) reacting at least a stoichiometrically equivalent amount of an
isocyanate blocking agent with the reaction product of (a) comprising
chain extended isocyanate-terminated polyurethane prepolymer to form a
blocked chain extended isocyanate-terminated polyurethane prepolymer;
wherein the ratio of the isocyanate groups of the polyisocyanate component
to the water solubilizing groups of the water solubilizing component is
such that the prepolymer can provide a stable dispersion upon combination
with a water phase;
(c) preparing a stable silyl-terminated polyurethane dispersion by
displacing the isocyanate blocking agent on the blocked chain extended
isocyanate-terminated polyurethane prepolymer of (b) by reacting under
sufficient agitation and at a sufficient temperature and pH the blocked
chain extended isocyanate terminated polyurethane prepolymer of (b) with a
water phase comprising:
(i) deionized water;
(ii) an isocyanate reactive silane compound having at least one active
hydrogen; and
(iii) a salt forming compound selected from the group consisting of basic
salt forming compounds and acidic salt forming compounds, wherein the salt
forming compound is selected such that the salt forming compound is
reactive with the water solubilizing group in the water solubilizing
compound which is reacted into the the chain extended polyurethane
prepolymer of (a), wherein some or all of the salt forming compound is
alternatively added to the mixture of step (a) or the mixture of step (b)
prior to combination of the blocked chain extended isocyanate terminated
polyurethane prepolymer with the water phase;
wherein a sufficient amount of the isocyanate reactive silane is present
relative to excess polyisocyanate component such that the active hydrogen
to isocyanate group ratio is about 0.85:1 to about 1: 1; and wherein the
optional polar organic coalescing solvent of element (a)(v) can optionally
be added to the water phase prior the formation of the dispersion.
A fifth method of making a hydrolyzable, silyl-terminated polyurethanes in
an aqueous dispersion comprises the steps of:
(a) reacting a mixture comprising:
(i) a polyol component comprising a compound having 2 isocyanate reactive
functional groups and optionally a compound having greater than 2
isocyanate reactive functional groups, each isocyanate reactive functional
group having at least one active hydrogen;
(ii) a water-solubilizing compound, wherein the water solubilizing compound
possesses at least one water solubilizing group and at least one
isocyanate reactive functional group, each isocyanate reactive functional
group containing at least one active hydrogen; and
(iii) a chain extender component comprising a difunctional chain extender
having 2 isocyanate reactive functional groups and optionally a
polyfunctional chain extender having at least 3 isocyanate reactive
functional groups, each isocyanate reactive functional group having at
least one active hydrogen;
(iv) a polyisocyanate component comprising a compound having 2 isocyanate
groups and optionally further comprising a compound having greater than 2
isocyanate groups wherein sufficient polyisocyanate component is included
to provide an excess on an isocyanate equivalent basis of about 1.4 to
about 4 times the combined active hydrogen equivalent of the isocyanate
reactive functional groups of the polyol component, the water solubilizing
compound, and the chain extender component;
(v) optional polar organic coalescing solvent; and
(vi) optional catalyst;
at a sufficient temperature in order to facilitate reaction of the mixture
to form a chain-extended isocyanate-terminated polyurethane prepolymer,
wherein the ratio of the isocyanate groups of the polyisocyanate component
to the water solubilizing groups of the water solubilizing component is
such that the prepolymer can provide a stable dispersion upon combination
with a water phase;
(b) reacting the chain extended isocyanate-terminated polyurethane
prepolymer of element (a) with an isocyanate-reactive silane compound
having at least one active hydrogen to produce a silyl-terminated
chain-extended polyurethane prepolymer;
wherein a sufficient amount of the isocyanate reactive silane compound is
present relative to excess polyisocyanate component such that the active
hydrogen to isocyanate group ratio is about 0.85:1 to about 1:1;
(c) preparing a stable silyl-terminated polyurethane dispersion by
combining under sufficient agitation and at a sufficient temperature and
pH the silyl-terminated chain extended isocyanate terminated polyurethane
prepolymer of (b) with a water phase comprising:
(i) deionized water;
(ii) a salt forming compound selected from the group consisting of basic
salt forming compounds and acidic salt forming compounds, wherein the salt
forming compound is selected such that the salt forming compound is
reactive with the water solubilizing group in the water solubilizing
compound which is reacted into the chain-extended isocyanate terminated
polyurethane prepolymer; wherein some or all of the salt forming compound
is alternatively added to the mixture of step (a) or the mixture of step
(b) prior to combination of the silyl-terminated chain-extended
polyurethane prepolymer with the water phase; wherein the optional polar
organic coalescing solvent of element (a)(v) can optionally be added to
the water phase prior the formation of the dispersion.
A sixth method of making a hydrolyzable, silyl-terminated polyurethane in
an aqueous dispersion comprises the steps of:
(a) reacting a mixture comprising:
(i) a polyol component comprising a compound having 2 isocyanate reactive
functional groups and optionally a compound having greater than 2
isocyanate reactive functional groups, each isocyanate reactive functional
group having at least one active hydrogen;
(ii) a water-solubilizing compound, wherein the water solubilizing compound
possesses at least one; water solubilizing group and at least one
isocyanate reactive functional group, each isocyanate reactive functional
group containing at least one active hydrogen;
(iii) a chain extender component comprising a difunctional chain extender
having 2 isocyanate reactive functional groups and optionally a
polyfunctional chain extender having at least 3 isocyanate reactive
functional groups, each isocyanate reactive functional group having at
least one active hydrogen;
(iv) a polyisocyanate component comprising a compound having 2 isocyanate
groups and optionally further comprising a compound having greater than 2
isocyanate groups wherein sufficient polyisocyanate component is included
to provide an excess on an isocyanate equivalent basis of about 1.4 to
about 4 times the combined active hydrogen equivalent of the isocyanate
reactive functional groups of the polyol component, the water solubilizing
compound, and the chain extender component;
(v) optional polar organic coalescing solvent; and
(vi) optional catalyst;
at a sufficient temperature in order to facilitate reaction of the mixture
to form a chain-extended isocyanate terminated polyurethane prepolymer,
wherein the ratio of the isocyanate groups of the polyisocyanate component
to the water solubilizing groups of the water solubilizing component is
such that the prepolymer can provide a stable dispersion upon combination
with a water phase;
(b) preparing a stable silyl-terminated polyurethane dispersion by
combining under sufficient agitation and at a sufficient temperature and
pH the chain extended isocyanate terminated polyurethane prepolymer of (a)
with a water phase comprising:
(i) deionized water;
(ii) a chain extender component comprising a difunctional chain extender
having 2 isocyanate reactive functional groups and optionally a
polyfunctional chain extender having at least 3 isocyanate reactive
functional groups, each isocyanate reactive functional group having at
least one active hydrogen;
(iii) an isocyanate reactive silane compound having at least one active
hydrogen; and
(iv) a salt forming compound selected from the group consisting of basic
salt forming compounds and acidic salt forming compounds, wherein the salt
forming compound is selected such that the salt forming compound is
reactive with the water solubilizing group(s) in the water solubilizing
compound, wherein some or all of the salt forming compound is
alternatively added to the mixture of step (a) prior to combination of the
chain extended isocyanate terminated polyurethane prepolymer with the
water phase;
wherein a sufficient amount of the chain extender component and the
isocyanate reactive silane compound is present relative to excess
polyisocyanate component such that the active hydrogen to isocyanate group
ratio is about 0.85:1 to about 1:1; wherein (a)(v) can optionally be added
to the water phase prior to the formation of the dispersion.
DETAILED DESCRIPTION OF THE INVENTION
The externally chain-extended silyl-terminated polyurethanes contained in
the dispersions of the invention are composed of several moieties.
Urethane moieties, optional urea moieties, and optional thiocarbamate
moieties link together generally divalent polyisocyanate-derived moieties,
polyol-derived moieties, chain extender-derived moieties, and solubilizing
moieties in the chain along with monovalent terminal silyl moieties.
Polyisocyanate-derived moieties are the radicals derived from
polyisocyanates having at least two isocyanate functional groups and
polyisocyanate adducts having at least two isocyanate functional groups by
the reaction of the isocyanate groups. Polyol-derived moieties are the
radicals formed by reaction of isocyanate-reactive functional groups on
the polyols. Similarly, chain extender-derived moieties are the radicals
derived from poly(active hydrogen), isocyanate-reactive organic compounds
(e.g., polyols, polyamines and polythiols). Water-solubilizing ionic
compounds and silyl compounds yield solubilizing moieties and silyl
moieties by elimination of isocyanate-reactive groups. The polyurethane
molecule as a whole is thus made up of recurring polyisocyanate-derived
moieties, polyol-derived moieties, chain extender derived moieties, and
interspersed solubilizing moieties, generally terminated by silyl
moieties. To some extent, of course, two or more molecules in aqueous
dispersion may be connected by siloxane linkages.
In general, the silane-terminated polyurethane dispersions are prepared by
first forming a polyurethane prepolymer by combining a polyisocyanate
component with isocyanate reactive compounds. This prepolymer is then
dispersed in a water phase which typically provides chain extension and
silane termination of the polyurethane prepolymer. A summary of basic
polyurethane chemistry and technology which explains and summarizes these
reactions and processes can be found, for example, in Polyurethanes:
Chemistry and Technology, Saunders and Frisch, Interscience Publishers
(New York, 1963 (Part I) and 1964 (Part II)).
The polyurethane prepolymers useful in the present invention can be
prepared by reacting an excess of a polyisocyanate component on an
isocyanate equivalent basis with one or more polyols and at least one
isocyanate-reactive water-solubilizing compound in the presence of an
optional catalyst and/or a coalescing solvent. One or more additional
optional components, such as chain extenders, blocking agents and
isocyanate-reactive silane compounds, may be included in the polyurethane
prepolymer. For example, isocyanate-terminated polyurethane prepolymers
may be modified to include a chain extender to form a chain extended
isocyanate-terminated polyurethane prepolymer, a blocking agent to form a
blocked isocyanate terminated polyurethane prepolymer, a polyfunctional
chain extender or polyisocyanate adduct to form a branched isocyanate
terminated polyurethane prepolymer, and/or an isocyanate-reactive silane
compound to form a silane-terminated polyurethane prepolymer.
In various instances multifunctional components with functionality greater
than two may be incorporated into the urethane dispersion in limited
amounts. Examples of these materials are: multifunctional polyols (e.g.,
TONE.TM. 0305, a trifunctional polyol available from Union Carbide),
polyisocyanates with functionality greater than two (e.g., DESMODUR.TM.
N-100, the biuret of hexamethylene diisocyanate available from Miles
Coating Division, a trifunctional isocyanate adduct such as Cythane.TM.
3160 based on TMXDI available from American Cyanamid), and multifunctional
chain extenders, (e.g., trimethylolpropane). The introduction of
multifunctional components may provide advantages to a coating made from
the finished dispersion such as improved solvent resistance. The
multifunctionality may cause a reduction in freeze-thaw stability when
incorporated in modestly high amounts. Generally if too much
multifunctionality is introduced, it may be difficult or impossible to
make a dispersion without some coagulation occurring.
The "urethane branching coefficient" (U.B.C.) is a calculation used to
express total the amount of branching provided by multifunctional
polyisocyanates, polyols and chain extenders in the urethane portion of
the silane-terminated urethane dispersion, i.e., it excludes the silane
linkage(s) (Si--O--Si) and (Si--OH) but will include other active hydrogen
groups of the silane such as amine, mercaptan, etc. The calculation
assumes unreacted isocyanate reacts with water.
Aminopropyltriethoxysilane, for example would have a branching coefficient
(B.C.) of 1. Similarly, diols and diisocyanates would each have a
branching coefficient of 2, triols and triisocyanates would each have a
branching coefficient of 3, etc. The urethane branching coefficient of a
silane-terminated urethane made with 1 mole of aminopropyltriethoxysilane,
1 mole of a diol, 2 moles of difunctional chain extender, 1 mole of triol,
and 5 moles of a diisocyanate would be calculated in this manner:
______________________________________
MOLE MOLE
MATERIAL B.C. MOLES % % B.C.
______________________________________
Aminopropyltriethoxysilane
1 1 0.1 0.1
Diol 2 1 0.1 0.2
Difunctional Chain Extender
2 2 0.2 0.4
Triol 3 1 0.1 0.3
Diisocyanate 2 5 0.5 1.0
URETHANE BRANCHING COEFFICIENT =
2.0
______________________________________
Using this measurement, the amount of branching in the silane-terminated
polyurethane dispersions of the present invention (the U.B.C.) typically
ranges from about 1.7 to about 2.25, preferably from about 1.85 to about
2.01.
It is important that the prepolymer prepared contain more than one
isocyanate radical in the reaction mixture for each active hydrogen
radical contributed by the polyol component, the water solubilizing
compound, and other isocyanate reactive compounds in the prepolymer.
"Active hydrogens" are those nucleophilic hydrogen atoms which conform to
the Zerewitinoff determination of hydrogen atoms; i.e., compounds which,
when reacted with a solution of methylmagnesium iodide in purified n-butyl
ether, produce methane. Typically, isocyanate reactive groups having at
least one active hydrogen include but are not limited to those selected
from the group consisting of --OH, NH.sub.2, --SH, and --NHR, wherein R is
selected from the group consisting of phenyl, straight or branched
aliphatic groups; comprising from about 1 to about 12 carbon atoms, and
cycloaliphatic groups. Isocyanate equivalent to active hydrogen equivalent
ratios of about 1.4:1 to about 4:1 are suitable in the polyurethane
prepolymers. Ratios of less than about 1.4:1 tend to produce films formed
from the polyurethane dispersions of the present invention which can have
low cohesive strength and are softer than desirable for most applications.
Ratios higher than about 4:1 provide a high combined chain
extender/isocyanate-reactive silane content when these components are
added in the water phase of the polyurethane dispersion. As a result, the
final coatings tend to be hard and stiff.
This required excess of isocyanate present in the prepolymer is then
consumed by condensation with the active-hydrogen containing isocyanate
reactive compounds in the water phase when the polyurethane prepolymer is
dispersed. If an external chain extender is introduced in the water phase
and little or no chain extension due to water is desired, then the
active-hydrogens contributed by either difunctional or polyfunctional
chain extenders typically represent on an equivalent basis from about 65
to about 95% on an equivalent basis of the excess of isocyanate, while the
isocyanate-reactive silane compound is present in the amount of about 5%
to about 30% of the excess isocyanate. If no chain extender is
incorporated in the water phase of the dispersion, then theoretically 100%
of the remaining isocyanate groups react with the active hydrogens found
in the isocyanate reactive silane compounds. However, if a minor degree of
chain extension due to water is desired, then from about 85 to about 100
percent, preferably about 95 to about 100 percent, of the isocyanate
excess can be reacted with the active hydrogens supplied by the chain
extenders and isocyanate reactive compounds. In this situation, the
remainder of the isocyanate excess can form urea linkages with other
prepolymers by a wellknown secondary reaction, first reacting with water
to form a carbamic acid which then converts to a primary amine and carbon
dioxide. This primary amine then forms a urea linkage with any available
isocyanate group in the dispersion.
The dispersions of the invention form useful and processible coatings at
solids content ranging from about 3 to about 45% by weight solids,
generally from about 3 to about 40% by weight solids.
Polyisocyanate
The polyisocyanate component must comprise a compound having two isocyanate
groups (i.e., diisocyanates and/or adducts thereof) and may optionally
comprise compounds having greater than 2 isocyanate groups (e.g.,
triisocyanates and/or adducts thereof). Adducts of the polyisocyanate
compounds as defined herein refer to isocyanate functional derivatives of
polyisocyanate compounds and polyisocyanate prepolymers. Examples of
adducts include but are not limited to those selected from the group
consisting of ureas, biurets, allophanates, dimers and trimers of
isocyanate compounds, uretonimediones, and mixtures thereof. Any suitable
organic polyisocyanate, such as an aliphatic, cycloaliphatic, araliphatic
or aromatic polyisocyanate, may be used either singly or in mixtures of
two or more. The aliphatic isocyanates provide generally better light
stability than the aromatic compounds. Aromatic polyisocyanates, on the
other hand, are generally more economical and reactive toward polyols and
other poly(active hydrogen) compounds than aliphatic polyisocyanates.
Suitable aromatic polyisocyanates include but are not limited to those
selected from the group consisting of 2,4-toluene diisocyanate,
2,6-toluene diisocyanate, a dimer of toluene diisocyanate (available under
the trademark Desmodur.TM. TT from Miles Coating Division),
diphenylmethane 4,4'-diisocyanate (MDI), 1,5-diisocyanato-naphthalene,
1,4-phenylene diisocyanate, 1,3-phenylene diisocyanate, and mixtures
thereof. Examples of useful cycloaliphatic polyisocyanates include but are
not limited to those selected from the group consisting of
dicyclohexylmethane diisocyanate (H.sub.12 MDI, commercially available as
Desmodur.TM.W from Miles Coating Division), isophorone diisocyanate
(IPDI), 1,4-cyclohexane diisocyanate (CHDI), 1,4-cyclohexanebis(methylene
isocyanate) (BDI), 1,3-bis(isocyanatomethyl)cyclohexane (H.sub.6 XDI), and
mixtures thereof. Examples of useful aliphatic polyisocyanates include but
are not limited to those selected from the group consisting of
hexamethylene 1,6-diisocyanate (HDI), 1,12-dodecane diisocyanate,
2,2,4-trimethyl-hexamethylene diisocyanate (TMDI),
2,4,4-trimethyl-hexamethylene diisocyanate (TMDI),
2-methyl-1,5-pentamethylene diisocyanate, dimer diisocyanate, the urea of
hexamethyl diisocyanate, and mixtures thereof. Examples of useful
araliphatic polysisocyanates include but are not limited to those selected
from the group consisting of m-tetramethyl xylylene diisocyanate
(m-TMXDI), p-tetramethyl xylylene diisocyanate (p-TMXDI), 1,4-xylylene
diisocyanate (XDI), 1,3-xylylene diisocyanate, and mixtures thereof.
Preferred polyisocyanates, in general, include those selected from the
group consisting of isophorone diisocyanate, toluene diisocyanate,
dicyclohexylmethane 4,4'-diisocyanate, MDI, derivatives of all the
aforementioned, and mixtures thereof.
Polyisocyanates or polyisocyanate adducts containing more than two
isocyanate groups in the molecule can be included to introduce branching
into the prepolymer which enhances the solvent resistance, water
resistance and hardness of coatings made from these polyurethane
dispersions; however, a predominance of diisocyanates is required. Limited
amounts of polyisocyanates containing greater than 2 isocyanate groups can
be employed subject to the urethane branching coefficient calculation
discussed previously. Typical isocyanates from this group include but are
not limited to those selected from the group consisting of
triphenylmethane 4,4',4"-triisocyanate,
tris-(4-isocyanatophenyl)-thiophosphate, and the like. Similarly, limited
amounts of polyisocyanate adducts containing more than two isocyanate
groups can be employed subject to the urethane branching coefficient
calculation discussed previously including but not limited to those
selected from the group consisting of trimer of isophorone diisocyanate
(Polyisocyanate IPDI-T 1890, commercially available from Huls America),
trimer of HDI (commercially available as Desmodur.TM.N3300 from Miles
Polymer Division), trimer of m-tetramethylxylene diisocyanate (a
trifunctional polyisocyanate adduct of trimethylolpropane and
m-tetramethylxylene diisocyanate available as Cythane.TM. 3160 from
American Cyanamid Co.).
The isocyanate-derived moiety of the polyurethane is thus a polyvalent
organic radical of from about 2 to about 40 carbon atoms free from
isocyanate-reactive or hydroxyl-reactive groups, e.g., --OH, --SH,
--NH.sub.2 --NHR, --CO.sub.2 H, --COCl, --SO.sub.3 H, --SO.sub.2 Cl, etc.,
wherein R is selected from the group consisting of phenyl, straight or
branched aliphatic groups comprising from about 1 to about 12 carbon
atoms, and cycloaliphatic groups. Preferably, R is a lower alkyl group
comprising 1 to 4 carbon atoms.
In addition, blocked polyisocyanates made from the above can be used. A
blocked polyisocyanate can be prepared by reacting one of the above
polyisocyanates with a blocking agent. Typical isocyanate blocking agents
include but are not limited to those selected from the group consisting of
phenol, nonyl phenol, methylethyl ketoxime, sodium bisulfate, and
.epsilon.-caprolactam. These blocked prepolymers can be used in
conjunction with diamines or diamine precursors such as ketamines.
Polyols
The polyol component comprises a compound having 2 isocyanate reactive
functional groups (diols and derivatives thereof) and optionally further
comprises a compound having greater than 2 isocyanate reactive groups
(triols, tetrols, etc. and/or derivative thereof), each isocyanate
reactive group having at least one active hydrogen.
Illustrative polyols include the following classes of compounds:
(i) the polyester polyols, including lactone polyols and the alkylene oxide
adducts thereof;
(ii) the polyether polyols, including polyoxyalkylene polyols,
polyoxycycloalkylene polyols, polythioethers, and alkylene oxide adducts
thereof; and
(iii) specialty polyols including but not limited to those selected from
the group consisting of polybutadiene polyols, hydrogenated polybutadiene
polyols, polycarbonate polyols, hydroxy alkyl derivatives of bisphenol A
such as bis(2-hydroxyethyl) bisphenol A, polythioether polyols,
fluorinated polyether polyols, amine-terminated polyether polyols, amine
terminated polyester polyols, and acrylic polyols.
The term "alkylene oxide" includes, for example, ethylene oxide,
1,2-epoxypropane, 1,2-epoxybutane, 2,3-epoxybutane, isobutylene oxide,
epichlorohydrin, mixtures thereof, and the like.
Preferred polyols are the polyester polyols and polyoxyalkylene polyols.
Polyester polyols are esterification products which range from liquids to
non-crosslinked solids, i.e., solids which are soluble in many of the more
common inert normally liquid organic media, and which are prepared by the
reaction of polycarboxylic acids, their anhydrides, their esters or their
halides, with a stoichiometric excess of a polyol. Preferred examples of
polycarboxylic acids which can be employed to prepare the polyester
polyols include dicarboxylic acids and tricarboxylic acids, such as maleic
acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic
acid, azelaic acid, sebacic acid, chlorendic acid,
1,2,4-butane-tricarboxylic acid, phthalic acid, terephthalic acid, and the
like. The esterification reaction followed in preparing polyester polyols
from polyfunctional acids and polyols is well known in the art. Examples
of specific useful polyester polyols include but are not limited to those
selected from the group consisting of polyglycol adipates, polyethylene
terephthalate polyols, polycaprolactone polyols.
Lactone polyols are known in the art and may be prepared, for example, by
reacting a lactone such as epsilon-caprolactone or a mixture of
epsilon-caprolactone and an alkylene oxide with a polyfunctional initiator
such as polyhydric alcohol. The term "lactone polyols" also includes the
various "copolymers" such as lactone copolyesters, lactone
polyester/polycarbonates, lactone polyester/polyethers, lactone
polyester/polyether/polycarbonates, and the like.
Polyether polyols include polyoxyalkylene polyols including alkylene oxide
adducts of, for example, water, ethylene glycol, diethylene glycol,
propylene glycol, butylene glycol, dipropylene glycol, glycerol,
polycaprolactone triols, tetra substituted hydroxypropyl ethylene diamine
available under the tradename Quadrol.TM. from BASF and the like. The
alkylene oxides employed in producing polyoxyalkylene polyols normally
comprise from 2 to 4 carbon atoms. Grafted polyether polyols such as
styrene/acrylonitrile grafted polyether polyols and Polyharnstoff
dispersion polyurea polyols, are also examples of useful polyether
polyols. Polyethylene oxide, propylene oxide and mixtures thereof are
preferred. Such polyalkylene polyols are well known in the art.
Another useful class of polyether polyols is the polyoxytetramethylene
glycols, which may be prepared, for example, by polymerizing
tetrahydrofuran in the presence of acidic catalyst. Random copolymers of
poly(tetramethylene oxide)/poly(ethylene oxide), such as those available
under the trademark PolyTHF.TM. ER1250 (commercially available from BASF),
are also useful polyether polyols. Examples of useful specific polyether
polyols include but are not limited to those selected from the group
consisting of poly(oxypropylene) glycols, ethylene oxide (eo) capped poly
(oxypropylene) glycol, .varies.,.omega.-diamino poly(oxypropylene),
aromatic amine-terminated poly(oxypropylene), graft-polyether polyols,
poly(oxyethylene) polyols, .alpha.,.omega.-diamino
poly(oxytetramethylene), polybutylene oxide polyols, poly(butylene
oxide-ethylene oxide) random copolymers, and mixtures thereof.
Other variants, adducts, and derivatives of polyether polyols, are useful
including but not limited to those selected from the group consisting of
amine-terminated polyoxyalkylene and polyoxymethylene compounds such as
.alpha.,.omega.-diamino poly(oxypropylene) glycol, POLAMINE.TM. (an
aromatic amine-terminated poly(oxytetramethylene) commercially available
from Air Products Co.), polythioether polyols such as LP series of
materials commercially available from Morton-Thiokol Co., fluorinated
polyether polyols, and mixtures thereof.
The molecular weight of the polyol component is one significant factor in
determining the final properties of the pollyurethane; generally, the
higher the molecular weight of the polyol component, the softer the
resulting polyurethane. The term "molecular weight" is used herein to
refer to the polyurethane. The term "molecular weight" is used herein to
refer to the number average molecular weight (M.sub.n). Polyols of
molecular weight as low as 250 and as high as about 35,000 produce useful
products, molecular weight ranges of about 500 to about 3000 being
preferred and most readily commercially available.
The polyol-derived moiety of the polyurethane is thus a polyvalent organic
radical of from about 10 to about 1000 carbon atoms free from
isocyanate-reactive or hydroxyl reactive groups.
Water-Solubilizing Compounds
Another component used in preparing the isocyanate terminated prepolymer is
a water-solubilizing compound. The water solubilizing compound possesses
at least one water solubilizing group and at least one isocyanate reactive
functional group, each isocyanate reactive functional group containing at
least one active hydrogen. Preferably, each compound has two isocyanate
reactive groups which are connected through an organic radical to each
other and to a water-solubilizing group. Suitable water-solubilizing
groups, such as carboxyl, sulfate, sulfonate, phosphorate, ammonium,
including quaternary ammonium, and the like, are those which ionize in
water when combined with a corresponding salt-forming compound. Preferred
isocyanate-reactive hydrogen atoms are those which react readily with an
isocyanate group at or below about 75.degree. C. such as the hydrogen
atoms of aliphatic hydroxyl, aliphatic mercapto, aliphatic amino, and
aromatic amino groups and are not those hydrogens present in the water
solubilizing group which could be considered active hydrogens under
certain circumstances. Hydrogen atoms which react slowly, such as the
"acidic" hydrogen atoms in amido groups, and sterically hindered or very
slow reacting acidic hydrogen atoms such as the carboxylic acid group of
dimethylpropionic acid are not included.
A suitable waterosolubilizing compound is represented by the formula
(HB).sub.2 R.sup.1 A in which R.sup.1 A is a water-solubilizing moiety; B
is selected from the group consisting of O, S, NH, and NR; R.sup.1
represents a trivalent organic linking group comprising about 2 to about
25 carbon atoms which may include tertiary nitrogen or ether oxygen atoms
and is free from isocyanate-reactive hydrogen containing groups; A is a
water solubilizing ionic group such as those selected from the group
consisting of --SO.sub.3 M, --OSO.sub.3 M, --CO.sub.2 M, --PO(OM).sub.3,
--NR.sub.2 .multidot.HX, and --NR.sub.3 X, wherein M is H or one
equivalent of a monovalent or divalent soluble cation such as sodium,
potassium, calcium, and NR.sub.3 .sup.H+, wherein X is a soluble anion
such as those selected from the group consisting of halide, hydroxide, and
deprotonated carboxylic acid, and R is selected from the group consisting
of a phenyl group, cycloaliphatic group, or a straight or branched
aliphatic group having from about 1 to about 12 carbon atoms. Preferably,
R is a lower alkyl group comprising 1 to 4 carbon atoms. The group
--NR.sub.3 X represents a quaternary ammonium substituent which is a salt
of water soluble acid, such as trimethyl ammonium chloride, pyridinium
sulfate, etc. or ammonium substituent and the group --NR.sub.2
.multidot.HX which is salt of a water soluble acid, such as dimethyl
ammonium acetate or propionate. A representative suitable solubilizing
molecule would be .alpha.,.alpha.-bis(hydroxymethyl) propionic acid
ammonium salt. The amount of water-solubilizing group provided should be
sufficient to self-emulsify the prepolymer, typically in the range of
isocyanate-to-solubilizing group ratio of from about 4:1 to about 16:1,
preferably at a proportion of from about 5:1 to about 11:1.
Illustrative solubilizing compounds include but are not limited to those
selected from the group consisting of:
##STR7##
Isocyanate-Reactive Silane Compounds
In addition to the isocyanate-terminated polyurethane prepolymer discussed
supra, isocyanate-reactive silane compounds are useful in forming the
dispersion of the invention. Silane compounds containing one, two, or
three hydrolyzable groups on the silicon and one organic group including
an isocyanate-reactive radical are most suitable for forming the terminal
groups. As has been pointed out above any of the conventional hydrolyzable
groups, such as those selected from the group consisting of hydrogen,
alkoxy, acyloxy, halogen, amino, oxime, and the like, can be used. The
hydrogen halide liberated from halogen-containing silanes may be
disadvantageous when cellulose substrates are used and amino containing
silazines are relatively unstable and difficult to handle. The alkoxy
group is the most preferred hydrolyzable group and particularly preferred
compounds are those of the structure (R.sup.30).sub.3 SiR.sup.4 --Z,
wherein (R.sup.30).sub.3 SiR.sup.4 -- is a silyl moiety, R.sup.3 is
selected from the group consisting of hydrogen, lower alkyl radicals of
one to four carbon atoms, preferably one or two (i.e., methoxy, ethoxy);
lower acyl groups of about 2 to about 5 carbon atoms, preferably 2 or 3
(i.e., acetyl or propionyl), and lower oxime groups of the formula
--N=CR.sup.5 R.sup.6, wherein R.sup.5 and R.sup.6 are monovalent lower
alkyl groups comprising about 1 to about 12 carbon atoms, which can be the
same or different, preferably selected from the group consisting of
methyl, ethyl, propyl, and butyl; R.sup.4 is a divalent organic bridging
radical of about 2 to about 20 carbon atoms free from isocyanate reactive
groups, preferably about 3 to about 10 carbon atoms, selected from the
group consisting of divalent hydrocarbyl radicals free from olefinic
unsaturation and free from isocyanate-reactive groups, and divalent
polyoxyalkylene mono- or poly-oxaalkylene radicals containing not more
than one ether oxygen per two carbon atoms; and Z is an isocyanate
reactive group such as those selected from the group consisting of --OH,
--SH, --NHR, --NH.sub.2, --N(C.sub.2 H.sub.4 OH).sub.2, and other active
hydrogen terminated compounds, wherein R is selected from the group
consisting of phenyl, straight or branched aliphatic groups comprising
from about 1 to about 12 carbon atoms, and cycloaliphatic groups.
Representative divalent alkylene radicals (i.e., R.sup.4) include but are
not limited to those selected from the group consisting of --CH.sub.2
CH.sub.2 --, --CH.sub.2 CH.sub.2 CH.sub.2 --, --CH.sub.2 CH.sub.2 CH.sub.2
OCH.sub.2 CH.sub.2 --, and --CH.sub.2 CH.sub.2 C.sub.6 H.sub.4 CH.sub.2
CH.sub.2 --. preferred compounds are those which contain one or two
hydrolyzable groups, such as those having the structures
##STR8##
wherein R.sup.3 and R.sup.4 are as previously defined.
Following the hydrolysis of some of these terminal silyl groups, the
polymers are curable by mutual interreaction to form siloxane linkages,
e.g.,
##STR9##
Such silicon compounds are well known in the art and many are commercially
available or are readily prepared. Representative isocyanate-reactive
silanes include but are not limited to those selected from the group
consisting of:
H.sub.2 NCH.sub.2 CH.sub.2 CH.sub.2 Si(OC.sub.2 H.sub.5).sub.3 ;
H.sub.2 NCH.sub.2 CH.sub.2 CH.sub.2 Si(OCH.sub.3).sub.3 ;
##STR10##
HSCH.sub.2 CH.sub.2 CH.sub.2 Si(OCH.sub.3).sub.3 ; HO(C.sub.2 H.sub.4
O).sub.3 C.sub.2 H.sub.4 N(CH.sub.3)(CH.sub.2).sub.3 Si(OC.sub.4
H.sub.9).sub.3 ;
H.sub.2 NCH.sub.2 C.sub.6 H.sub.4 CH.sub.2 CH.sub.2 Si(OCH.sub.3).sub.3 ;
HSCH.sub.2 CH.sub.2 CH.sub.2 Si(OCOCH.sub.3).sub.3 ;
HN(CH.sub.3)CH.sub.2 CH.sub.2 Si(OCH.sub.3).sub.3 ;
HSCH.sub.2 CH.sub.2 CH.sub.2 SiCH.sub.3 (OCH.sub.3).sub.2 ;
(H.sub.3 CO).sub.3 SiCH.sub.2 CH.sub.2 CH.sub.2 NHCH.sub.2 CH.sub.2
CH.sub.2 Si(OCH.sub.3).sub.3 ;
and mixtures thereof.
Salt-Forming Compounds
When acidic functional water-solubilizing compounds are employed in the
isocyanate-terminated prepolymer, basic salt-forming compounds, such as
tertiary amines, inorganic bases including but not limited to those
selected from the group consisting of sodium hydroxide, potassium
hydroxide, cesium hydroxide, lithium hydroxide, calcium hydroxide,
magnesium hydroxide, zinc hydroxide, and barium hydroxide are used in a
sufficient amount (i.e., in a quantity to maintain a pH of greater than
about 8) preferably in the water phase, but optionally in the preparation
of the prepolymer, to anionically stabilize the dispersions of the present
invention through the formation of salts with the incorporated, pendant
acidic water-solubilizing groups on the resultant polyurethane. Examples
of useful salt-forming compounds include but are not limited to those
selected from the group consisting of ammonia, trimethylamine,
triethylamine, tripropylamine, triisopropylamine, tributylamine,
triethanolamine, diethanolamine, and mixtures thereof. Preferred salt
forming compounds include those selected from the group consisting of
ammonia, trimethylamine, triethylamine, tripropylamine, and
triisopropylamine, since dispersions containing polyurethanes prepared
therefrom are less hydrophilic upon coating and cure.
When an amine functional or other basic water-solubilizing compound is
used, the polyurethane dispersions preferably maintain a pH of less than
about 6 to be cationically stabilized. Examples of useful acidic compounds
include but are not limited to those: selected from the group consisting
of acetic acid, formic acid, citric acid, octanoic acid, phenols and
substituted phenols, hydrochloric acid, hydrobromic acid, hydrofluoric
acid, and mixtures thereof. These acidic salt-forming compounds are
generally a component of the water phase when the polyurethane dispersions
of the present invention are prepared; however, they may alternatively be
added to the polyurethane prepolymer prior to the dispersion of the
prepolymer in the water phase.
However, when straight chain aliphatic or aromatic compounds containing 2
or more isocyanate groups are used it is preferred to add the salt forming
compound to the water phase. Certain salts formed by the reaction of salt
forming compounds and water solubilizing groups such as potassium
hydroxide in combination with a carboxylic acid solubilizing group could
result in an undesired isocyanate reaction.
IV. Chain Extenders
The term "chain extender" as used herein includes external chain extenders
and blocked external chain extenders such as ketamines and oxazolines. The
term chain extender as used refers to externally added chain extenders and
excludes those generated in situ. Thus, the chain extension resulting from
the reaction of the polyisocyanate compounds with the water of the water
phase of the polyurethane dispersions is not denoted by this term and
water is not considered an "external" chain extender. Chain extenders are
employed to enhance the mechanical properties of the polyurethane of the
present invention. Polyols and polyamines useful as chain extenders as the
term is used herein are those usually having a number average molecular
weight of about 249 or less. The chain extender component must comprise a
difunctional chain extender and may optionally comprise a chain extender
having a functionality of three or greater. Generally, due to the kinetics
involved in the prepolymer and dispersion stages of the methods of the
present invention, it is preferable to incorporate hydroxy functional
chain extenders in the prepolymer and primary amine functional chain
extenders in the water phase when preparing the silyl-terminated
polyurethane dispersions. Through proper and judicious selection of
reaction conditions, starting materials and additives known in the
polyurethane art, such as blocked amines, catalysts, temperature, etc.,
reaction kinetics can be adapted to allow for the use of primary amines in
the prepolymer reaction mixture and hydroxy functional chain extenders in
the water phase.
Difunctional Chain Extenders
Examples of useful diol chain extenders include but are not limited to
those selected from the group consisting of 1,4-butanediol, ethylene
glycol, diethylene glycol, dipropylene glycol, neopentyl glycol,
1,6-hexanediol, 1,4-cyclohexane dimethanol,
bis(2-hydroxylethyl)hydroquinone (HQEE), and mixtures thereof.
Difunctional sterically hindered amines are included in the definition of
"difunctional chain extender" as used herein except for the difunctional
sterically hindered amines of formula II set forth below.
Difunctional sterically hindered amines having the general formula
##STR11##
wherein: R.sup.7, R.sup.8, R.sup.9 are independently selected from the
group consisting of cyclic and aliphatic organic radicals free of
isocyanate reactive functional groups, and with the proviso that at least
75% of the R.sup.9 groups have at least 4 carbon atoms; are specifically
excluded from the difunctional chain extenders useful according to the
present invention. Specific examples of these excluded amines are the
following: phenyldiethanolamine, n-butyldiethanolamine, etc.
Examples of useful diamine chain extenders include but are not limited to
those selected from the group consisting of 4,4'-methylene
bis(o-chloroaniline)(MOCA or MBOCA), 2,5-diethyl-2,4-toluene diamine
(DETDA), 4,4'-methylene bis(3-chloro-2,6-diethylaniline)(MCDEA), propylene
glycol bis(4,4'-aminobenzoate), 3,5-di(thiomethyl)-2,4-toluene diamine,
methylene bis(4,4'-aniline)(MDA), ethyl-1,2-di(2-amino thiophenol),
4-chloro-3,5-diamino isobutylbenzoate, 1,2-diaminoethane,
1,4-diaminobutane, 1,6-diaminohexane, N,N'-dialkyl(methylene dianiline),
N,N'-dialkyl(1,4-diaminobenzene), and mixtures thereof.
Polyfunctional Chain Extenders
Chain extenders and/or chain extender adducts having more than two
isocyanate reactive functional groups, each functional group in the
molecule having at least one active hydrogen (i.e., polyfunctional chain
extenders) can be included in the polymer; however, difunctional chain
extenders are required. Thus triols, tetrols, etc., can be used to
introduce branching into the polyurethanes of the invention. These
polyfunctional chain extenders are preferably low molecular weight and
best utilized with short chain extenders such as 1,4-butanediol or the
chain extenders as described infra. Small amounts of branching in the
polyurethane backbone improve tensile strength and solvent resistance and
decrease cold-flow of the final coatings prepared from the dispersions of
the invention. On the other hand, excessive amounts of branching in the
polyurethane of the dispersion cause poor flow and thus less desirable
film formation, freeze/thaw stability and processibility. Examples of
useful polyfunctional chain extenders include but are not limited to those
selected from the group consisting of 1,2,6-hexanetriol,
1,1,1-trimethylolethane or propane, pentaerythritol, triisopropanol amine,
and triethanol amine.
Catalysts
The polyurethane prepolymer compositions of the present invention may be
prepared without the use of a catalyst when the reaction is performed at a
sufficient temperature (i.e., about 20.degree. to about 100.degree. C.) to
cause the reaction between the polyisocyanate component and the active
hydrogen containing compounds of the polyurethane prepolymer mixture.
However, a catalyst may optionally be used according to the method of the
invention. Depending on reaction conditions (e.g., reaction temperature
and/or polyisocyanate used), a catalyst at the level of up to about 0.5
part by weight of the isocyanate-terminated prepolymer typically about
0.00005 to about 0.5 part by weight may be required to form the prepolymer
by the methods of the present invention. Examples of useful catalysts
include but are not limited to those selected from the group consisting of
tin II and IV salts such as stannous octoate and dibutyltin dilaurate,
respectively, tertiary amine compounds such as triethyl amine and
bis(dimethylaminoethyl) ether, morpholine compounds such as
.beta.,.beta.'-dimorpholinodiethyl ether, bismuth carboxylates,
zinc-bismuth carboxylates, iron (III) chloride, potassium octoate, and
potassium acetate. Examples of other useful catalysts can also be found in
Polyurethanes: Chemistry and Technology, Part I, Table 30, Chapter 4,
Saunders and Frisch, Interscience Publishers, New York, 1963.
Solvents
Although the polyurethanes of the present invention can be prepared without
the use of solvents, solvents can be used to control the viscosity of the
isocyanate-terminated prepolymer. Examples of useful solvents (which are
typically volatile organic compounds) added for this purpose include but
are not limited to those selected from the group consisting of ketones,
tertiary alcohols, ethers, esters, amides, hydrocarbons,
chlorohydrocarbons, chlorocarbons, and mixtures thereof. These are usually
stripped at the end of the reaction by vacuum heating.
Solvents may also be required to promote the coalescence of the
silyl-terminated polyurethane particles of the dispersion to form a
continuous film. Examples of such coalescing solvents for use in the
dispersion include but are not limited to those selected from the group
consisting of n-methyl pyrrolidinone (NMP), n-butyl acetate, dimethyl
formamide, toluene, methoxypropanol acetate (PM acetate), dimethyl
sulfoxide (DMSO), ketones, alcohols, dimethyl acetamide, and mixtures
thereof.
A polyurethane prepolymer is prepared in the first step of the process of
making the silyl-terminated polyurethane dispersions of the present
invention. To a reactor equipped with a stirrer, a heater, and a dry gas
purge (for example, nitrogen, argon, etc.), the polyisocyanate component
is added to the reactor with optional coalescing solvent and optional dry
solvent (e.g. anhydrous methylethyl ketone, having H.sub.2 O levels of
0.05% or less). The reactor is heated to the reaction temperature
(generally from about 20.degree. C. to about 100.degree. C.) and the
polyol component, optional catalyst, and the water solubilizing compound
is added slowly, keeping the reaction exotherm below 100.degree. C. to
minimize unwanted side reactions. Optionally all or a portion of the chain
extender component and the isocyanate reactive silane compound can be
added at this point. If such optional compounds are included, then the
isocyanate reactive functional groups on the chain extender and silane
should not contain large amounts of a primary amine because there can be
an unacceptable viscosity increase in the prepolymer which could make the
dispersion step in water difficult.
As the polyurethane prepolymer is made, additional chain extender and
polyisocyanate components can optionally be incorporated into the reaction
mixture. In a preferred embodiment of the present method, a polyisocyanate
adduct having greater than 2 isocyanate groups can be added after about
80% of the polyisocyanate, polyol and optional chain extender components
have converted to the prepolymer. The reaction is then allowed to proceed
until the desired excess on an isocyanate equivalent basis of about 1.4 to
about 4 times the combined active hydrogen equivalent as contributed by
the polyol component, the water solubilizing compound, and optional chain
extender component and isocyanate reactive silane compound is achieved.
Optionally the salt forming compound can be added to this polyurethane
prepolymer reaction mixture. If the salt forming compound is added, care
should be taken to reduce temperature and/or disperse the polyurethane
prepolymer in the water phase shortly after this addition. The product of
the salt forming compound with the water-solubilizing compound can produce
a salt which may in some cases catalyze an unwanted side reaction. This
side reaction could result in an undesired viscosity increase making the
dispersion step difficult. This rise in viscosity can be minimized or
avoided by taking the precautions listed above. Optional solvent can be
added at this point to modify the viscosity and/or enhance the
processibility of the polyurethane prepolymer. The viscosity of the
prepolymer should be low enough (about 70,000 cps or less) to facilitate
the dispersion step.
The second step is to make a water phase. The water phase typically
comprises water, the salt forming compound, and all or the remainder of
the chain extender component and the isocyanate reactive silane compound.
Deionized water is used to prevent instability and agglomeration of the
polyurethane prepolymer when it is subsequently dispersed into the water
phase. Primary amine functional chain extenders and isocyanate reactive
silane compounds are preferred in the water phase due to their relatively
rapid reactivity with the isocyanate groups of the polyurethane
prepolymer. If the final amount of the chain extender component,
isocyanate reactive silane compound or salt forming compound has been
added previously to the prepolymer, then they need not be added to the
water phase. If partial additions of these components and compounds have
occurred in the prepolymer, the remaining material may be added to the
water phase, assuming compatibility with the water can be achieved, i.e.,
the components are either water soluble or water dispersible. The pH of
the water phase is then measured to assure that the dispersion will be
stable. For cationic dispersions, enough salt forming compound is added to
assure that the dispersion will be stable. Usually a pH of about 6 or
lower is required, with a pH of about 4.5 or less preferred. An anionic
dispersion is adjusted to achieve a pH of about 7 or higher, preferably a
pH of about 8 or more.
The third step is to disperse the polyurethane prepolymer of the first step
into the water phase of the second step. The water phase is added to the
holding tank of a homogenizer and sufficient air pressure is supplied to
pump the water phase through the homogenizer's high shear rotor. The
polyurethane prepolymer is slowly injected into the circulating water
phase just prior to the high shear rotor. Care should be taken not to
inject material too quickly or the high shear rotor will stop the
dispersion process. The dispersed material is then transferred back into
the water phase holding tank. On the average two or three passes through
the homogenizer typically yields a mean particle size in the range of
about 0.06 to about 0.3 microns. However, particle size can vary with
equipment, viscosity, presence of solvent temperature, etc. The particle
size can be controlled by the viscosity of the first step. The higher the
viscosity, generally the larger the particle size.
Introduction of solvents into polyurethane prepolymer reaction mixture will
have the result of lowering the particle size. If such an optional solvent
was introduced, e.g., methylethyl ketone, the final step would be to strip
off the unwanted solvent. This can be accomplished using a wiped film
evaporator which applies heat and vacuum to a thin film of the material
efficiently stripping off the solvent. Under laboratory conditions, a
Haake Rotoevaporator or other similar equipment can be used to remove the
solvent.
Optional Additives
One or more additives may be added to the dispersion of the invention
including but not limited to those selected from the group consisting of
crosslinking agents, plasticizers, thixotropic agents, biocides, adhesion
promoters such as silane adhesion promoters, corrosion inhibitors,
pigments, colorants, photostabilizers, antioxidants, and anti-fouling
agents. To further enhance the moisture resistivity of the formulated
silane terminated polyurethane dispersions about 0 to about 5 parts by
weight of a crosslinking agent, preferably about 3 to about 5 parts by
weight, based upon 100 parts by weight of the dispersion may be added.
Many salt forming compounds contribute to the hydrophilicity of coatings
containing polyurethanes prepared therefrom. The crosslinker makes the
coating containing such a polyurethane more hydrophobic.
Particularly useful additives in the wood coating formulations of the
present invention include but are not limited to defoaming agents such as
Surfynol.TM. DF110L (a high molecular weight acetylenic glycol nonionic
surfactant available from Air Products & Chemicals, Inc.), SWS-211 (a
polydimethylsiloxane aqueous emulsion, available from Wacker Silicone
Corp.), Dehydran.TM. 1620 (modified polyol/polysiloxane adducts available
from Henkel Corp.), and DB-31 (a silicone additive available from Dow
Corning), and DB-65 (a silicone additive available from Dow Corning); mar
aids such as Byk.RTM. 301, Byk.RTM. 321 and Byk.RTM. 341 (polyether
modified polydisiloxane copolymers, all available from Byk Chemie); flow
and levelling agents such as Igepal.TM. CO-630 (an ethoxylated nonylphenol
nonionic surfactant available from Rhone-Poulenc Surfactant & Specialty
Div.), Surfynol.TM. 104H (a nonionic surfactant comprising a solution of
tetramethyl decynediol in ethylene glycol available from Air Products &
Chemicals, Inc.), Surfynol.TM. 465 (an ethoxylated tetramethyl decynediol
nonionic surfactant available from Air Products & Chemicals, Inc.),
Fluorad.TM. FC-129 (a potassium fluorinated alkyl carboxylate anionic
surfactant available from 3M Co.), Fluorad.TM. FC-171 (a fluorinated alkyl
alkoxylate nonionic surfactant available from 3M Co.), Fluorad FC-430 (a
fluorinated alkyl ester nonionic surfactant available from 3M Co.), and
Rexol.TM. 25/9 (an alkyl phenol ethoxylate nonionic surfactant available
from Hart Chemical Ltd.); coalescing solvents such as those described
supra to assist in film formation; thickening agents such as the
associative thickeners Acrysol.TM. ASE-60, Acrysol.TM. RM-825, Acrysol.TM.
TT-935 and Acrysol.TM. 615, all available from Rohm and Haas Co.; and
photostabilizers including but not limited to ultraviolet light (UV)
stabilizers such as Tinuvin.TM. 144 (a hindered amine photostabilizer),
Tinuvin.TM. 292 (a hindered amine photostabilizer) and Tinuvin.TM. 328 (an
ultraviolet absorber), all commercially available from Ciba-Geigy Ltd. For
marine wood coatings of the present invention which are often subject to
intense UV exposure, at least about 0.1 part by weight of an ultraviolet
light stabilizer per 100 parts by weight silyl-terminated polyurethane
dispersion can be used to inhibit and retard the yellowing and
photodegradation of such formulations, typically about 0.1 to about 10
parts, preferably about 1 to about 10 parts.
Uses
The dispersions of the invention can be coated on a variety of substrates
to form high gloss, water and solvent resistant, tough, scratch resistant,
preferably light stable (non-yellowing) films.
Substrates such as leather, woven and nonwoven webs, glass, glass fibers,
wood (including oil woods such as teak, etc.), metals (such as aluminum),
treated metal such as primed and painted metals (such as those comprising
automobile and marine surfaces), polymeric materials and surfaces, such as
plastics (appliance cabinets, for example) etc., can be coated with the
dispersions or films.
The composition of the invention has utility as an intermediate coating. It
is generally applied over the several primer and sealer layers (well known
to those skilled in the art) used to coat metal (including primed metal
and painted metal), plastic, and fiber-reinforced plastic composite
substrates used in the fabrication of vehicular bodyparts and appliance
cabinets. Vehicular bodyparts include, for example, hoods, fender,
bumpers, grills, rocker panels and the like; and appliance cabinets
include, for example, washers, clothes dryers, refrigerators, and the
like. Examples of vehicles on which the compositions can be used include
automobiles, trucks, bicycles, airplanes, etc. The composition of the
invention can be used as an intermediate coating because it is applied
under top/finish coatings which typically comprise paints, enamels, and
lacquers and the like that in many cases are chemically crosslinked to
provide durable, scratch-resistant surface finishes. The composition of
the invention adheres to most body filler compositions and thus also has
utility in the autobody repair trade.
The composition of the invention can also be coated onto composite
materials, such as fiber reinforced plastics wherein the plastics are
toughened by the addition of glass, boron, graphite, ceramic, or
dissimilar polymer fibers; and filled plastics wherein the ;plastic
properties are modified by the addition of inorganic powders, (such as
calcium carbonate, talc, titanium dioxide, carbon black, etc.), flakes
(such as aluminum, mica, etc.), and microspheres/beads (such as glass or
polymeric). The composition of the invention can be coated onto a number
of articles such as vehicular body parts and appliance cabinets.
The compositions of the invention may also be coated on surfaces such as
concrete, asphalt, etc. (roadways, patios, sidewalks, etc.). An adhesive
backed pavement marking tape may be adhered thereto.
Compositions of the present invention for use as UV stabilized coatings
such as furniture and/or marine finishes can be formulated to retard or
eliminate the effects of UV degradation by combining cycloaliphatic
isocyanates, such as isophorone and bis(cyclohexyl)diisocyanate, with UV
stabilizers and antioxidants. Moisture adsorption/permeation can be
minimized by the use of the relatively more hydrophobic polyester based
polyols. Coating elasticity can be controlled by adjusting the isocyanate
equivalent to active hydrogen ratio, chain extender content and the
crosslink density of the cured film. The crosslink density can be
controlled by adjusting such parameters as the urethane branching
coefficient and molecular weight per crosslink.
The UV stabilized coating composition of the invention comprises about 85
to about 99.9% by weight dispersion of the invention, about 0.1 to about
10% by weight of a photostabilizer, about 0 to about 10% by weight of a
surfactant, and about 0 to about 10% by weight of a thickening agent based
upon the total weight of the coating composition, and total 100%.
Preferably the wood coating composition comprises about 90 to about 97% by
weight dispersion of the invention, and 0.2 to about 5% by weight
photostabilizer, about 0.1 to about 6% by weight of a surfactant, and
about 0.1 to about 1% by weight of a thickening agent based upon the total
weight of the coating composition. Most preferably, the wood coating
composition of the invention comprises about 92 to about 96 percent by
weight dispersion of the invention, about 1 to about 3% by weight
photostabilizer, about 1 to about 5% by weight surfactant and about 0.1 to
about 0.5 percent by weight thickening agent, based upon the total weight
of the coating composition.
The use of the dispersion of the, present invention as a component in a
chip-resistant coating composition, is disclosed in copending concurrently
filed U.S. application Ser. No. 08/109,671, now abandoned Holland et al.,
entitled "One-Part Storage. Stable Water Dispersible Poly(Urethane/Urea)
Chip-Resistant Coatings".
Test Methods
Stability
The long term stability of the polyurethane dispersions was assessed both
at room temperature (23.degree. C.) and at elevated temperature
(71.degree. C.) according to a modification of American Society for
Testing and Measurement (ASTM) Test Method D 1791-87. A 100 mL sample of
polyurethane dispersion was placed in a clean, dry test bottle. The test
bottle was then capped and inverted and placed in either a drying oven
capable of maintaining a temperature of the dispersion at 71.degree. C. or
in a device capable of maintaining room temperature. At the end of a
30-day storage period, the sample dispersions rated "good" were those
which did not gel or separate over that storage period. Samples
dispersions rated "poor" gelled or separated over this 30-day period under
these storage conditions.
Viscosity Measurements The bulk viscosity of each polyurethane dispersion
was determined by using Brookfield Viscometer Model RVF. Approximately 1
liter of the dispersion was poured into the chamber and placed in the
thermostat. The measurement was taken after thermal equilibrium was
reached. Spindles #1-#4 were used depending on the viscosity of the
sample. The data are included in Table 1.
Water/Solvent Resistance
A 2".times.3" rectangular area on an unpolished, cold rolled, 10.16 cm (4
inch).times.30.48 cm (12 inch).times.0.0126 cm (0.032 inch) steel test
panel (available from Advanced Coating Technologies, Inc. as test panel
BEPI P60 DIW) was coated with the polyurethane dispersion. The dispersion
was then cured on the test panels for 7 days at 21 .degree. C. and 50%
relative humidity. The dried film thickness was approximately 100 .mu.m (4
mils). About 1/3 of the coating was immersed in deionized water at
21.degree. C. with no water circulation. After 8 hrs. the panels were
removed from the water, dried and visually inspected for blistering,
swelling, loss of adhesion or any other visually discernable changes. The
above procedure was repeated by immersing the coated steel test panels in
a solvent (methyl ethyl ketone).
Mechanical Properties
Mechanical testing (i.e., tensile and elongation) was performed on an
Sintech Model 10 tensile tester. Testing was performed according to a
modification of American Society for Testing and Measurement (ASTM) Test
Method D 412-87. Samples were prepared according to Method A (dumbbell and
straight specimens) of this test method. Dumbbell specimens approximately
0.318 cm (0.125 inch) in width and approximately 0.159 cm (0.0625 inch) in
thickness (cross-sectional area of approximately 0.05 1 cm.sup.2) were
tested at a crosshead speed of 5.08 cm/min (2 inches/min) and the results
of these measurements recorded and listed in Table 1.
Adhesion to Wood
The adhesion of polyurethane wood finishes prepared from polyurethane
dispersions to wood test panels was measured according to a modification
of Method B of American Society for Testing and Measurement (ASTM) Test
Method D3359-83. Oak plywood panels 0,635 cm (1/4 inch) in thickness which
were pretreated with an acrylate based sealer (High Bond Sealer
commercially available from Bona Kemi USA Inc.) and then coated with a
polyurethane finish (3-4 coats applied using a brush, allowing a minimum
of 45 minutes dry time and light sanding with 120 grit sandpaper between
coats). The dried cured polyurethane coating was approximately 125 .mu.m
in thickness. Using a razor blade, 6 cuts of about 20 mm in length spaced
2 mm apart were made in the cured coating, followed by similarly spaced
cuts at 90.degree. to and centered on the original cuts. An about 75 mm
piece of a transparent cellophane pressure-sensitive adhesive tape (610
tape, commercially available from 3M Co.) was placed in firm contact with
the cross-cut area, allowed to dwell for about 90 seconds on the sample,
and peeled rapidly from the cross-cut area at approximately 180.degree..
The cross-cut grid area was then examined under magnification and rated
using the following scale:
5B The edges of the cuts were completely smooth; none of the squares of the
lattice is detached.
4B Small flakes of the coating were detached at intersections; less than 5%
of the area was affected.
3B Small flakes of the coating were detached along edges and at
intersections of cuts. The area affected was 5 to 15% of the lattice.
2B The coating was flaked along the edges and on parts of the squares. The
area affected was 15 to 35% of the lattice.
1B The coating was flaked along the edges of cuts in large ribbons and
whole squares were detached. The area affected was 35 to 65% of the
lattice.
0B Flaking and detachment were worse than grade 1B.
Impact Resistance
The impact resistance of wood panels coated with a polyurethane finish
prepared from the polyurethane dispersions of the present invention was
measured in the following manner: Oak plywood panels 0.635 cm (1/4 inch)
in thickness were pretreated with an acrylate based sealer (High Bond
Sealer commercially available from Bona Kemi USA Inc.) and then coated
with a polyurethane finish (3-4 coats applied using a brush, allowing a
minimum of 45 minutes dry time and light sanding with 120 grit sandpaper
between coats). The dried cured polyurethane coating was approximately 125
.mu.m in thickness. A 500 gram stainless steel rod was dropped through a
cylinder from set distances. The rod hits the impinger which in turn hits
the coated panels. The distance in centimeters at which the impact of this
500 gram rod on coatings did not cause any crack of the coatings was
recorded.
Taber Abrasion
Wood finishes prepared from the polyurethane dispersions of the present
invention were coated (3-4 coats applied using a brush, allowing a minimum
of 45 minutes dry time and light sanding with 120 grit sandpaper between
coats) on laminated kitchen counter tops and cured for 6 weeks at
21.degree. C. (Formica.TM. high pressure laminated sheets of melamine and
phenolic plastics). These coatings were subjected to abrasion using either
H-22 wheel, 500 gm weight or CS-17 wheel, 1 kg weight for 50-1000 cycles.
The amount of weight loss from these coatings due to abrasion of these
wheels in a Taber abrader was determined by weighing the samples before
and after abrasion and weight loss was recorded. This test provides
information on wear properties of coatings and is an indirect measurement
of durability.
Solvent Resistance
The solvent resistance of wood finishes prepared from the polyurethane
dispersions of the present invention was measured in the following manner:
Oak plywood panels 0.635 cm (3/4 inch) in thickness were pretreated with
an acrylate based sealer (High Bond Sealer commercially available from
Bona Kemi USA Inc.) and then coated with a polyurethane finish (3-4 coats
applied using a brush, allowing a minimum of 45 minutes dry time and light
sanding with 120 grit sandpaper between coats). The dried cured
polyurethane coating was approximately 125 .mu.m in thickness. The coated
test panels were allowed to cure at ambient conditions (21.degree. C. and
60-75% relative humidity) for six weeks. Paper dots having a diameter of
0.953 cm (3/8 inch) were applied on the coated surface and the dots were
saturated with 14 different test solvents, including 100% methyl ethyl
ketone, a range of binary mixtures of ethanol and water or methyl ethyl
ketone and water, and ternary mixtures of ethanol, methyl ethyl ketone and
water. The dots were then dried for four hours. The following rating
scheme for solvent resistance was applied:
2 points--paper dots were removed cleanly from the coatings;
1 point--paper dots removed, but paper residue was left on the coating;
and,
0 point--paper dots did not remove from the coating.
According to this test method, the maximum attainable rating was a score of
28.
Gloss
The gloss of wood finishes prepared from the polyurethane dispersions of
the present invention was measured in the following manner: Oak plywood
panels 0.635 cm (3/4 inch) in thickness were pretreated with an acrylate
based sealer (High Bond Sealer commercially available from Bona Kemi USA
Inc.) and then coated with a polyurethane finish (3-4 coats applied using
a brush, allowing a minimum of 45 minutes dry time and light sanding with
120 grit sandpaper between coats). The dried cured polyurethane coating
was approximately 125 .mu.m in thickness. The gloss of such prepared
polyurethane finish surfaces was then measured using a reflectometer
(Lange Reflectometer, Model RB-60) against a calibration standard at a
60.degree. angle of reflection. The calibration standard was a polished,
high gloss plate defined in accordance with the stipulations of DIN 67530.
Stain Resistance
The stain resistance of wood finishes prepared from the polyurethane
dispersions of the present invention was measured in the following manner
in accordance with ANSI A 161.1-1985 ("Recommended Performance Standard
for Kitchen and Vanity Cabinets"): Oak plywood panels 0.635 cm (3/4 inch)
in thickness were pretreated with a sealer (typically High Bond Sealer
commercially available from Bona Kemi USA Inc.) and then coated with a
polyurethane finish (3-4 coats applied using a brush, allowing a minimum
of 45 minutes dry time and light sanding with 120 grit sandpaper between
coats). The dried cured polyurethane coating was approximately 125 .mu.m
in thickness. 3 cc samples of vinegar, lemon juice, grape juice, tomato
catsup, coffee, milk, were applied to the polyurethane wood finishes for
24 hours and then wiped off and examined for stain development. Similarly,
3 cc samples of mustard, permanent marker and 3% ammonia were applied to
the sample finishes, removed after one hour, and the finish was examined
for stain development from these samples. Stain resistance was ranked
according to the following scale: 2 points for no indication of these
staining agents and 0 points for any degree of staining. Thus, the maximum
recorded stain resistance ranking according to this test method is 22.
Weathering Resistance
The weathering resistance of wood finishes prepared from the polyurethane
dispersions of the present invention was measured in the following manner
in accordance with American Society for Testing and Materials (ASTM) Test
Method G-26 ("Standard Practice for Operating Light-Exposure Apparatus
(Xenon-Arc Type) With and Without Water Exposure of Nonmetallic
Materials"): Teak panels 30.5 cm (12 inches) in length, 3.81 cm (1.5
inches) in width and 0.318 cm (0.375 inch) in thickness were coated with a
polyurethane finish (3 coats applied using a soft brush, allowing a
minimum of 1 hour dry time between coats). Although not required, each
coating can be followed by light sanding with a 600 grit sandpaper between
coats; however, at least 4 hours must be allowed between sanding: and the
application of a subsequent coat. For comparative solventborne coatings,
at least 24 hours between sanding and application of the next coat was
required. All examples were then allowed to cure for one week at room
temperature (21.degree. C.) and 50% relative humidity and cut into six 5
cm test sections.
The coated test sections were then placed in a xenon-arc light-exposure
apparatus as described in Test Method A ("Continuous Exposure to Light and
Intermittent Exposure to Water Spray") of ASTM--G 26 (1988) using a Type
BH humidity controlled light-exposure device and exposed to repeated
cycles of 102 minutes of light from this xenon-arc source, followed by a
18 minute cycle of light and water spray. A black panel temperature of
63.degree. C. was maintained throughout the test. For each coating sample,
a coated teak wood test section was then removed from the test apparatus
at 250, 500, 1000, 2000 and 3000 hours and the weathering of the coating
was assessed and recorded.
______________________________________
ABBREVIATIONS
______________________________________
A-1110 .gamma.-aminopropyltrimethoxysilane com-
mercially available from OSi
AA acetic acid
Cythane .TM. 3160
a trifunctional polyisocyanate adduct of
trimethylolpropane and m-tetramethylxylene
diisocyanate, commercially available from
American Cyanamid Co.
DES W 4,4-cyclohexylmethyl diisocyanate com-
mercially available from Miles Coating
Division under the tradename
"Desmodur W"
DMPA .alpha.,.alpha.-(bishydroxy methyl) propionic acid
EDA 1,2-diaminoethane
Excess NCO an excess on an isocyanate equivalent basis
when compared to the combined active
hydrogen equivalent of other components
in the polyurethane prepolymer
or dispersion
eq. equivalent
HCA hydrocaffeic acid
IPDI isophorone diisocyanate
Irganox .TM. 245
a hindered phenolic antioxidant com-
mercially available from Ciba-Geigy Ltd.
Irganox .TM. 1010
a hindered phenolic antioxidant com-
mercially available from Ciba-Geigy Ltd.
LEX1130-30 Lexorez .TM. 1130-30, a linear poly(1,6-
hexanediol-adipate) of 1870 average
equivalent weight commercially
available from Inolex
LEX1130-55 Lexorez .TM. 1130-55, a linear poly(1,6-
hexanediol-adipate) of 1020
average equivalent weight
commercially available from Inolex
LEX1400-35 Lexorez .TM. 1400-35, a linear poly(1,6-
hexanediol-neopentyl glycol-adipate)
of 1600 average equivalent weight
commercially available from Inolex
LEX1400-120 Lexorez .TM. 1400-120, a linear poly(1,6-
hexanediol-neopentyl glycol-adipate)
of 470 average equivalent
weight commercially available from Inolex
MDEA methyldiethanol amine
MEK methyl ethyl ketone
NCO/OH molar ratio of isocyanate to hydroxy groups
NMP n-methyl pyrrolidone
ARCOL .TM. 2025
poly(oxypropylene) glycol of 1000 average
equivalent weight commercially available
from ARCO Chemical.
Silane Q2-8038
.gamma.-aminopropylmethyl dimethoxysilane
commercially available from Dow
Corning Co.
T-9 a stannous octanoate catalyst commercially
available from Air Products Co.
T-12 a dibutyltin dilaurate catalyst commercially
available from Air Products Co.
TDI toluene diisocyanate
TEA triethylamine
2000thane .TM.
a poly(tetramethylene ether glycol) of
1000 average equivalent weight
commercially available from duPont
Tinuvin .TM. 144
a hindered amine photostabilizer com-
mercially available from
Ciba-Geigy Ltd.
Tinuvin .TM. 292
a hindered amine photostabilizer com-
mercially available from Ciba-Geigy Ltd.
Tinuvin .TM. 328
an ultraviolet absorber commercially
available from Ciba-Geigy Ltd.
TMP 1,1,1-trimethylolpropane
Tone .TM. 201
a caprolactone-based diol of 265 average
equivalent weight commercially available
from Union Carbide Chemicals and
Plastics Co.
Tone .TM. 210
a caprolactone-based diol of 425 average
equivalent weight commercially available
from Union Carbide Chemicals and
Plastics Co.
Tone .TM. 230
a caprolactone-based diol of 623 average
equivalent weight commercially available
from Union Carbide Chemicals and
Plastics Co.
Tone .TM. 260
a caprolactone-based diol of 1500 average
equivalent weight commercially available
from Union Carbide Chemicals and
Plastics Co.
______________________________________
EXAMPLES
The invention is further illustrated by the following nonlimiting examples.
All parts, percentages, ratios, etc. in the examples and the rest of the
specification are by weight unless otherwise specified.
Example 1
A prepolymer was made in a 1 liter reaction flask equipped with a heating
mantel, condenser, stirring blade, nitrogen inlet and thermometer equipped
with a temperature controller. 308.23 grams (2.3351 eq.) of
4,4'-cyclohexylmethane diisocyanate (DES W), 360.72 grams (0.5787 eq.) of
Tone.TM. 230 (a caprolactone-based polyol), 40.10 grams (0.5976 eq.) of
2,2-bis(hydroxymethyl) propionic acid (DMPA) and 125.10 grams of n-methyl
pyrrolidone (NMP) were heated with stirring to 40.degree.-50.degree. C.
0.081 gram of dibutyl tin dilaurate (T-12) was added and the mixture was
heated to 80.degree. C. and allowed to react for 2 hours.
A premix was made with 325.00 grams of distilled water, 5.28 grams of
triethylamine (TEA), 6.00 grams (0.1997 eq.) of EDA and 6.00 grams (0.0335
eq.) of gamma-aminopropyltrimethoxysilane (A-1110).
170.15 grams (0.2363 eq.) of the prepolymer was added over 10 minutes to
the premix solution in a Microfluidics Homogenizer Model # HC-5000 at an
air line pressure of 0.621 MPa. A stable dispersion was formed, pH and
viscosity were recorded, and the dispersion was subjected to both room
temperature (RT) and elevated temperature (71.degree. C.) stability
testing. The dispersion was then cured for 1 week at 70.degree. F. and 50%
Relative Humidity (R.H.) and the cured composition's water resistance,
solvent (methyl ethyl ketone) resistance, tensile strength, and elongation
was measured. These properties were recorded and can be found in Table 1.
The U.B.C. was calculated to be 1.868.
Comparative Example C-1
Comparative Example C-1 was prepared according to the "Best Mode of the
Invention" in U.S. Pat. No. 4,582,873 (Gaa et al.) with a few minor
variations. The silylated isocyanate-containing-prepolymer was prepared in
an anhydrous reaction conducted in the presence of a solvent and a
catalyst. A slight nitrogen blanket was maintained during the reaction. To
a clean and dry kettle reactor having an agitator there was added 236.50
grams of the polyester diol commercially available under the trade
designation "Tone 200" from Union Carbide Corporation. This material has a
molecular weight of around 530 and was premelted at 180.degree. C. Also
added was 10.20 grams of the hydrophilic ethylene oxide-containing
material, which is a polyoxyethylene polyol homopolymer available under
the trade designation "Carbowax 1450" material. This material is also
available from Union Carbide Corporation and was also premelted at
180.degree. C. Also added was 1.24 grams of 1,4-butanediol as the
hardening segment polyol. The difunctional organosilane,
N-(.beta.-aminoethyl), .gamma.-aminopropyl trimethoxysilane available from
Union Carbide Corporation under the trade designation "A-1120" was added
in an amount of 4.59 grams. As a solvent n-methyl-pyrrolidone (NMP) was
added in an amount of 46.05 grams. These materials were heated to
140.degree. F. (60.degree. C.).
Over a period of 30 minutes while the temperature was maintained between
140.degree. F. (60.degree. C.) to 150.degree. F. (66.degree. C.), 258.35 g
of methylene-bis-(4-cyclohexyl isocyanate) were added to the kettle
reactor with agitation. This cycloaliphatic diisocyanate is available
under the trade designation Desmodur W material from Miles Coating
Division. An additional amount of NMP (35.15 g) was used to rinse the
beaker and added to the mixture. This mixture was held at 140.degree. F.
(60.degree. C.) to 150.degree. F. (66.degree. C.) for 10 minutes.
An amount of 26.75 grams of DMPA was added and the temperature was
maintained between 170.degree. F. (77.degree. C.) and 175.degree. F.
(79.degree. C.) for 30 minutes.
0.25 grams of the catalyst dibutyl tin dilaurate was added. The temperature
was held at 170.degree. F.-175.degree. F. until a constant NCO equivalent
of around 1045 to 1087 was obtained.
An amount of 15.20 grams of n-methyl pyrrolidone was added while cooling to
160.degree.-165.degree. F. Over 10 minutes, 20.20 grams of triethylamine
were added to neutralize the mixture. The beaker was rinsed with 2.25 g
NMP which was then added to the mixture.
A premix was made with 9.04 grams ethylenediamine and 526.44 grams of
water.
340.30 grams of the prepolymer was injected into the premix in a
Microfluidics Homogenizer Model #HC-5000 at an air line pressure of 0.621
mPa over a period of 10 minutes. The amounts arid types of neutralizer and
chain extender used in the production of the aqueous dispersion of the
chain-extended polymer gave the dispersion a pH of 8.3. No particles
formed in the dispersion. The viscosity of the dispersion was 32,000
centipoise.
Comparative Example C-2
Comparative Example C-2 was prepared according to Example I of U.S. Pat.
No. 3,941,733 (Chang) with a few minor variations. Into a 2-liter
round-bottom glass flask equipped for heating, cooling, agitation and
vacuum stripping were charged 675.15 grams of polyoxypropylene diol
(average equivalent wt. 490) and 17.15 grams of polyoxypropylene triol
(average equivalent wt. 137). A vacuum was applied and the solution was
heated to 130.degree.-140.degree. C. for 30 minutes. The solution was then
cooled to 40.degree. C. and 235.30 grams of toluene diisocyanate (80:20
percent mixture of 2,4-toluene diisocyanate and 2,6-toluene diisocyanate)
were added. The solution temperature increased to 65.degree.-70.degree. C.
and was maintained in that range for 2 hours. To the reaction mixture was
added 0.15 grams of a 25% solution of stannous octoate in dioctyl
phthalate and stirring was continued, temperature being maintained at
65.degree.-70.degree. C. for an additional 3 hours. The solution was
cooled to 60.degree.-65.degree. C. and diluted with 100.00 grams of methyl
ethyl ketone to decrease the viscosity.
A solution of isocyanate-reactive water-soluble salt was prepared by
dissolving 72.18 grams of the triethylamine salt of
.alpha.,.alpha.-bis(hydroxymethyl) propionic acid in 21.21 grams of methyl
ethyl ketone.
To 1027.75 grams of the vigorously stirred intermediate prepolymer solution
under a dry nitrogen blanket are added 18.69 grams of an
isocyanate-reactive trialkoxysilane, triethoxysilylpropyl amine H.sub.2
N(CH.sub.2).sub.3 Si(OC.sub.2 H.sub.2).sub.3 and mixed 10-15 minutes
followed by 93.39 grams of the above triethylamine salt solution. Stirring
is continued for 2 minutes followed by the addition of 15 g MEK. A 340.30
gram aliquot of the reaction mixture is dispersed in 557.86 grams water in
the range of 20.degree.-65.degree. C. by a high-shear mechanical
homogenizer (Microfluidics Homogenizer Model #HC-5000 at an air line
pressure or 0.621 MPa).
Example 2
A prepolymer having a lower molecular weight polyester polyol segment was
made in a 1 liter reaction flask equipped with a heating mantel,
condenser, stirring blade, nitrogen inlet and thermometer equipped with a
temperature controller to monitor temperature. 426.78 grams (3.233 eq.) of
4,4'-cyclohexylmethane diisocyanate (DES W), 212.40 grams (0.8015 eq.) of
Tone.TM. 201 (a caprolactone-based polyol), 55.53 grams (0.8276 eq.) of
2,2-bis(hydroxymethyl) propionic acid (DMPA) and 122.76 grams of n-methyl
pyrrolidone (NMP) were heated with stirring to 40.degree.-50.degree. C.
0.112 gram of dibutyl tin dilaurate (T-12) was added and the mixture was
heated to 80.degree. C. and allowed to react for 2 hours.
A premix was made with 325.00 grams of distilled water, 7.48 grams of
triethylamine (TEA), 8.50 grams (0.2829 eq.) of ethylene diamine (EDA) and
8.50 grams (0.0474 eq.) of gamma-aminopropyltrimethoxysilane (A-1110).
170.15 grams (0.3338 eq.) of the prepolymer was added over 10 minutes to
the premix solution in a Microfluidics Homogenizer Model #HC-5000 at an
air line pressure of 0.621 MPa. A stable dispersion was formed, pH and
viscosity were recorded, and the dispersion was subjected to both room
temperature (RT) and elevated temperature (71.degree. C.) stability
testing. The dispersion was then cured for 1 week at 70.degree. F. and 50%
Relative Humidity (R.H.) to a thickness of 4 mils and the cured
composition's water resistance, solvent (methyl ethyl ketone) resistance,
tensile strength, and elongation was measured. These properties were
recorded and can be found in Table 1. The U.B.C. was calculated to be
1.867.
Example 3
A prepolymer having a high molecular weight polyester polyol was made in a
1 liter reaction flask equipped with a heating mantel, condenser, stirring
blade, nitrogen inlet and thermometer equipped with a temperature
controller to monitor temperature. 151.74 grams (1.1495 eq.) of
4,4'-cyclohexylmethane diisocyanate (DES W), 427.37 grams (0.2849 eq.) of
Tone.TM. 260 (a caprolactone-based polyol), 19.74 grams (0.2942 eq.) of
2,2-bis(hydroxymethyl) propionic acid (DMPA) and 257.60 grams of n-methyl
pyrrolidone (NMP) were heated with stirring to 40.degree.-50.degree. C.
0.040 gram of dibutyl tin dilaurate (T-12) was added and the mixture was
heated to 80.degree. C. and allowed to react for 2 hours.
A premix was made with 325.00 grams of distilled water, 2.51 grams of
triethylamine (TEA), 2.85 grams (0.0948 eq.) of ethylene diamine (EDA) and
2.85 grams (0.0159 eq.) of gamma-aminopropyltrimethoxysilane (A-1110).
170.15 grams (0.1133 eq.) of the prepolymer was added over 10 minutes to
the premix solution in a Microfluidics Homogenizer Model #HC-5000 at an
air line pressure of 0.621 MPa. A stable dispersion was formed, pH and
viscosity were recorded, and the dispersion was subjected to both room
temperature (RT) and elevated temperature (71.degree. C.) stability
testing. The dispersion was then cured for 1 week at 70.degree. F. and 50%
Relative Humidity (R.H.) to a thickness of 4 mils and the cured
composition's water resistance, solvent (methyl ethyl ketone) resistance,
tensile strength, and elongation was measured. These properties were
recorded and can be found in Table 1. The U.B.C. was calculated to be
1.869.
Example 4
A prepolymer having lower solubilizing acid content was made in a 1 liter
reaction flask equipped with a heating mantel, condenser, stirring blade,
nitrogen inlet and thermometer equipped with a temperature controller to
monitor temperature. 284.52 grams (2.1555 eq.) of 4,4'-cyclohexylmethane
diisocyanate (DES W), 418.86 grams (0.6720 eq.) of Tone.TM. 230 (a
caprolactone-based polyol), 27.77 grams (0.4139 eq.) of
2,2-bis(hydroxymethyl) propionic acid (DMPA) and 129.00 grams of n-methyl
pyrrolidone (NMP) were heated with stirring to 40.degree.-50.degree. C.
0.075 gram of dibutyl tin dilaurate (T-12) was added and the mixture was
heated to 80.degree. C. and allowed to react for 2 hours.
A premix was made with 322.00 grams of distilled water, 4.75 grams of
triethylamine (TEA), 4.80 grams (0.1797 eq.) of ethylene diamine (EDA) and
5.40 grams (0.0301 eq.) of gamma-aminopropyltrimethoxysilane (A-1110).
170.15 grams (0.2116 eq.) of the prepolymer was added over 10 minutes to
the premix solution in a Microfluidics Homogenizer Model #HC-5000 at an
air line pressure of 0.621 MPa. A stable dispersion was formed, pH and
viscosity were recorded, and the dispersion was subjected to both room
temperature (RT) and elevated temperature (71.degree. C.) stability
testing. The dispersion was then cured for 1 week at 70.degree. F. and 50%
Relative Humidity (R.H.) to a thickness of 4 mils and the cured
composition's water resistance, solvent (methyl ethyl ketone) resistance,
tensile strength, and elongation was measured. These properties were
recorded and can be found in Table 1. The U.B.C. was calculated to be
1.867.
Example 5
A prepolymer having higher solubilizing acid content was made in a 1 liter
reaction flask equipped with a heating mantel, condenser, stirring blade,
nitrogen inlet and thermometer equipped with a temperature controller to
monitor temperature. 403.07 grams (3.0536 eq.) of 4,4'-cyclohexylmethane
diisocyanate (DES W), 228.06 grams (0.3659 eq.) of Tone.TM. 230 (a
caprolactone-based polyol), 78.68 grams (1.17:26 eq.) of
2,2-bis(hydroxymethyl) propionic acid (DMPA) and 304.00 grams of n-methyl
pyrrolidone (NMP) were heated with stirring to 40.degree.-50.degree. C.
0.106 gram of dibutyl tin dilaurate (T-12) was added and the mixture was
heated to 80.degree. C. and allowed to react for 2 hours.
A premix was made with 248.00 grams of distilled water, 5.72 grams of
triethylamine (TEA), 6.50 grams (0.2163 eq.) of ethylene diamine (EDA) and
6.50 grams (0.0363 eq.) of gamma-aminopropyltrimethoxysilane (A-1110).
170.15 grams (0.2543 eq.) of the prepolymer was added over 10 minutes to
the premix solution in a Microfluidics Homogenizer Model #HC-5000 at an
air line pressure of 0.621 MPa. A stable dispersion was formed, pH and
viscosity were recorded, and the dispersion was subjected to both room
temperature (RT) and elevated temperature (71.degree. C.) stability
testing. The dispersion was then cured for 1 week at 70.degree. F. and 50%
Relative Humidity (R.H.) to a thickness of 4 mils and the cured
composition's water resistance, solvent (methyl ethyl ketone) resistance,
tensile strength, and elongation was measured. These properties were
recorded and can be found in Table 1. The U.B.C. was calculated to be
1.867.
Comparative Example C-3
A prepolymer having insufficient solubilizing acid (DMPA) content was made
in a 1 liter reaction flask equipped with a heating mantel, condenser,
stirring blade, nitrogen inlet and thermometer equipped with a temperature
controller to monitor temperature. 237.1 grams (1.7962 eq.) of
4,4'-cyclohexylmethane diisocyanate (DES W), 420.76 grams (0.6750 eq.) of
Tone 230 (a caprolactone-based polyol), 15.42 grams (0.2298 eq.) of
2,2-bis(hydroxymethyl) propionic acid (DMPA) and 119.00 grams of n-methyl
pyrrolidone (NMP) were heated with stirring to 40.degree.-50.degree. C.
0.0625 gram of dibutyl tin dilaurate (T-12) was added and the mixture was
heated to 80.degree. C. and allowed to react for 2 hours.
A premix was made with 318.00 grams of distilled water, 4.31 grams of
triethylamine (TEA), 4.90 grams (0.1631 eq.) of ethylene diamine (EDA) and
4.9 grams (0.0273 eq.) of gamma-aminopropyltrimethoxysilane (A-1110).
170.15 grams (0.19 14 eq.) of the prepolymer was added over 10 minutes to
the premix solution in a Microfluidics Homogenizer Model #HC-5000 at an
air line pressure of 0.621 MPa. The polyurethane dispersion was initially
stable, but some of the dispersion settled to the bottom after 5 days
storage at room temperature due to partial agglomeration of the
dispersion. The U.B.C. was calculated to be 1.867.
Comparative Example C-4
A prepolymer having no polyester polyol and an excess of solubilizing acid
was made in a 1 liter reaction flask equipped with a heating mantel,
condenser, stirring blade, nitrogen inlet and thermometer equipped with a
temperature controller to monitor temperature. 483.68 grams (3.6642 eq.)
of 4,4'-cyclohexylmethane diisocyanate (DES W), 123.88 grams (1.8462 eq.)
of 2,2-bis(hydroxymethyl) propionic acid (DMPA).and 260.4 grams of
n-methyl pyrrolidone (NMP) were heated with stirring to
40.degree.-50.degree. C. 0.127 gram of dibutyl tin dilaurate (T-12) was
added and the mixture was heated to 80.degree. C. and allowed to react for
2 hours.
A premix was made with 264.00 grams of distilled water, 7.97 grams of
triethylamine (TEA), 9.1 grams (0.3028 eq.) of ethylene diamine (EDA) and
9.1 grams (0.0508 eq.) of gamma-aminopropyltrimethoxysilane (A-1110).
170.15 grams (0.3563 eq.) of the prepolymer was added over 10 minutes to
the premix solution in a Microfluidics Homogenizer Model #HC-5000 at an
air line pressure of 0.621 MPa. The material gelled during emulsification.
The U.B.C. was calculated to be 1.867.
Comparative Example C-5
A prepolymer having an excess of diisocyanate (NCO/OH=5) was made in a 1
liter reaction flask equipped with a heating mantel, condenser, stirring
blade, nitrogen inlet and thermometer equipped with a temperature
controller to monitor temperature. 459.92 grams (3.4842 eq.) of
4,4'-cyclohexylmethane diisocyanate (DES W), 213.66 grams (0.3428 eq.) of
Tone 230 (a caprolactone-based polyol), 23.75 grams (0.3539 eq.) of
2,2-bis(hydroxymethyl) propionic acid (DMPA) and 122.43 grams of n-methyl
pyrrolidone (NMP) were heated with stirring to 40.degree.-50.degree. C.
0.048 gram of dibutyl tin dilaurate (T-12) was added and the mixture was
heated to 80.degree. C. and allowed to react for 2 hours.
A premix was made with 475.00 grams of distilled water, 12.94 grams of
triethylamine (TEA), 6.0 grams (0.1997 eq.) of ethylene diamine (EDA) and
67.3 grams (0.3753 eq.) of gamma-aminopropyltrimethoxysilane (A-1110).
170.15 grams (0.5785 eq.) of the prepolymer was added over 10 minutes to
the premix solution in a Microfluidics Homogenizer Model #HC-5000 at an
air line pressure of 0.621 MPa. The material gelled during emulsification.
The U.B.C. was calculated to be 1.510.
Example 6
A low molecular weight urethane polymer (average molecular weight 4800) was
prepared by emulsifying the 170.15 grams (0.2363 eq.) of the prepolymer of
Example 1 with a premix consisting of 340.00 grams of distilled water,
5.28 grams of triethylamine (TEA), 4.67 grams (0.1554 eq.) of ethylene
diamine (EDA) and 13.93 grams (0.0777 eq.) of
gamma-aminopropyltrimethoxysilane (A-1110). A stable dispersion was
formed, pH and viscosity were recorded, and the. dispersion was subjected
to both room temperature (RT) and elevated temperature (71.degree. C.)
stability testing. The dispersion was then cured for 1 week at 70.degree.
F. and 50% Relative Humidity (R.H.) to a thickness of 4 mils and the cured
composition's water resistance, solvent (methyl ethyl ketone) resistance,
tensile strength, and elongation was measured. These properties were
recorded and can be found in Table 1. The U.B.C. was calculated to be
1.718.
Example 7
A high molecular weight (average molecular weight 100,000) was prepared by
emulsifying the 170.15 grams (0.2363 eq.) of the prepolymer of Example 1
with a premix consisting of 316.00 grams of distilled water, 5.28 grams of
triethylamine (TEA), 6.90 grams (0.2296 eq.) of ethylenediamine (EDA) and
0.64 gram (0.0036 eq.) of gamma-aminopropyltrimethoxysilane (A-1110). A
stable dispersion was formed, pH and viscosity were recorded, and the
dispersion was subjected to both room temperature (RT) and elevated
temperature (71.degree. C.) stability testing. The dispersion was then
cured for 1 week at 70.degree. F. and 50% Relative Humidity (R.H.) to a
thickness of 4 mils and the cured composition's water resistance, solvent
(methyl ethyl ketone) resistance, tensile strength, and elongation was
measured. These properties were recorded and can be found in Table 1. The
U.B.C. was calculated to be 1.985.
Comparative Example C-6
A urethane polymer of very low molecular weight (average molecular weight
3300) was prepared by emulsifying the 170.15 grams (0.2363 eq.) of the
prepolymer of Example 1 with a premix consisting of 351.00 grams of
distilled water, 5.28 grams of triethylamine (TEA), 3.55 grams (1181 eq.)
of ethylene diamine (EDA) and 20.6 grams (0.1149 eq.) of
gamma-aminopropyltrimethoxysilane (A-1110). A stable dispersion was not
formed. The prepolymer immediately agglomerated upon mixing with the water
phase. The U.B.C. was calculated to be 1.609.
Example 8
A prepolymer having higher catalyst and solvent content was made using only
the heat generated from the exotherm (e.g., no external heat added,
maximum temperature from the exotherm=70.degree. C.) in a 1 liter reaction
flask equipped with a condenser, stirring blade, nitrogen inlet and
thermometer. 308.23 grams (2.335 1 eq.) of 4,4'-cyclohexylmethane
diisocyanate (DES W), 360.72 grams (0.5787 eq.) of Tone.TM. 230 (a
caprolactone-based polyol), 40.10 grams (0.5976 eq.) of
2,2-bis(hydroxymethyl) propionic acid (DMPA), 305.50 grams of n-methyl
pyrrolidone (NMP), and 4.16 grams of dibutyl tin dilaurate (T-12) were
combined and the mixture was allowed to react for 2 hours.
A premix was made with 238.00 grams of distilled water, 4.32 grams of
triethylamine (TEA), 4.90 grams (0.1631 eq.) of ethylene diamine (EDA) and
4.90 grams (0.0273 eq.) of gamma-aminopropyltrimethoxysilane (A-1110).
170.15 grams (0.1935 eq.) of the prepolymer was added over 10 minutes to
the premix solution in a Microfluidics Homogenizer Model #HC-5000 at an
air line pressure of 0.621 MPa. A stable dispersion was formed, pH and
viscosity were recorded, and the dispersion was subjected to both room
temperature (RT) and elevated temperature (71.degree. C.) stability
testing. The dispersion was then cured for 1 week at 70.degree. F. and 50%
Relative Humidity (R.H.) to a thickness of 4 mils and the cured
composition's water resistance, solvent (methyl ethyl ketone) resistance.
tensile strength, and elongation was measured. These properties were
recorded and can be found in Table 1. The U.B.C. was calculated to be
1.868.
Example 9
A prepolymer was made using an alternative catalyst (i.e. triethylamine) in
a 1 liter reaction flask equipped with a heating mantel, condenser,
stirring blade, nitrogen inlet and thermometer equipped with a temperature
controller to monitor temperature. 308.23 grams (2.3351 eq.) of
4,4'-cyclohexylmethane diisocyanate (DES W), 360.72 grams (0.5787 eq.) of
Tone.TM. 230 (a caprolactone-based polyol), 40.10 grams (0.5976 eq.) of
2,2-bis(hydroxymethyl) propionic acid (DMPA) and 125.10 grams of n-methyl
pyrrolidone (NMP) were heated with stirring to 40.degree.-50.degree. C.
4.16 grams of triethylamine (TEA) was added and the mixture was heated to
80.degree. C. and allowed to react for 2 hours.
A premix was made with 325.00 grams of distilled water, 5.28 grams of
triethylamine (TEA), 6.00 grams (0.1997 eq.) of ethylene diamine (EDA) and
6.00 grams (0.0335 eq.) of gamma-aminopropyltrimethoxysilane (A-1110).
170.15 grams (0.2352 eq.) of the prepolymer was added over 10 minutes to
the premix solution in a Microfluidics Homogenizer Model #HC-5000 at an
air line pressure of 0.621 MPa. A stable dispersion was formed, pH and
viscosity were recorded, and the dispersion was subjected to both room
temperature (RT) and elevated temperature (71.degree. C.) stability
testing. The dispersion was then cured for 1 week at 70.degree. F. and 50%
Relative Humidity (R.H.) to a thickness of 4 mils and the cured
composition's water resistance, solvent (methyl ethyl ketone) resistance,
tensile strength, and elongation was measured. These properties were
recorded and can be found in Table Y. The U.B.C. was calculated to be
1..867.
Example 10
A prepolymer was made using an alternative solubilizing compound (i.e.,
methyldiethanol amine) in a 1 liter reaction flask equipped with a heating
mantel, condenser, stirring blade, nitrogen inlet and thermometer equipped
with a temperature controller to monitor temperature. 308.23 grams (2.3351
eq.) of 4,4'-cyclohexylmethane diisocyanate (DES W), 360.72 grams (0.5787
eq.)of Tone.TM. 230 (a caprolactone-based polyol), 35.61 grams (0.5976
eq.) of methyldiethanol amine (MDEA) and 124.30 grams of n-methyl
pyrrolidone (NMP) were heated with stirring to 40.degree.-50.degree. C.
0.081 gram of dibutyl tin dilaurate (T-12) was added and the mixture was
heated to 80.degree. C. and allowed to react for 2 hours.
To a 170.15 gram (0.2378 eq.) aliquot of the prepolymer at 50.degree. C.
was added 10.00 grams methyl ethyl ketone (MEK) and 25.00 grams (0.8326
eq.) glacial acetic acid (0.8326 eq.). This prepolymer mixture was then
emulsified in 200.00 grams of distilled water.
A premix was made with 125.00 grams of distilled water, 25.00 grams of
acetic acid, 6.00 grams (0.1997 eq.) of ethylene diamine (EDA) and 6.00
grams (0.0335 eq.) of gamma-aminopropyltrimethoxysilane (A-1110).
Dropwise and with stirring, 162.00 grams of the premix was added to 405.15
grams of the prepolymer dispersion. The MEK was then stripped off under
heat and vacuum. A stable dispersion was formed, pH and viscosity were
recorded, and the dispersion was subjected to both room temperature (RT)
and elevated temperature (71.degree. C.) stability testing. A pH of 4.5
was measured and a viscosity of 10 cps. The U.B.C. was calculated to be
1.868.
Example 11
A prepolymer was made using an alternative solubilizing compound (i.e.,
hydrocaffeic acid) in a 1 liter reaction flask equipped with a heating
mantel, condenser, stirring blade, nitrogen inlet and thermometer equipped
with a temperature controller to monitor: temperature. 308.23 grams
(2.3351 eq.) of 4,4'-cyclohexylmethane diisocyanate (DES W), 382.00 grams
(0.6129 eq.) of Tone.TM. 230 (a caprolactone-based polyol), 51.25 grams
(0.5626 eq.) of hydrocaffeic acid (HCA) and 130.80 grams of n-methyl
pyrrolidone (NMP) were heated with stirring to 40.degree.-50.degree. C.
0.081 grams of dibutyl tin dilaurate (T-12) was added and the mixture was
heated to 80.degree. C. and allowed to react for 2 hours.
To a 170.15 gram (0.2262 eq.) aliquot of the prepolymer at 50.degree. C.
was added 10.00 grams methyl ethyl ketone (MEK) and 5.28 grams
triethylamine. This prepolymer mixture was then emulsified in 200.00 grams
of distilled water.
A premix was made with 125.00 grams of distilled water, 5.75 grams (0.1913
eq.) of ethylene diamine (EDA), and 5.75 grams (0.0321 eq.) of
gamma-aminopropyltrimethoxysilane (A-1110 ).
Dropwise and with stirring 136.50 grams of the premix was added to 385.43
grams of the prepolymer dispersion. The MEK was then stripped off under
heat and vacuum. The dispersion remained stable for 5 days at a recorded
pH of 10.5. The U.B.C. was calculated to be 1.867.
Example 12
A prepolymer was made in a 1 liter reaction flask equipped with a heating
mantel, condenser, stirring blade, nitrogen inlet and thermometer equipped
with a temperature controller to monitor temperature. 200.00 grams (1.8002
eq.) of isophorone diisocyanate (IPDI), 277.48 grams (0.4452 eq.) of
Tone.TM. 230 (a caprolactone-based polyol), 30.83 grams (0.4598 eq.) of
2,2-bis(hydroxymethyl) propionic acid (DMPA) and 225.00 grams of methyl
ethyl ketone (MEK) were heated with stirring to 40.degree.-50.degree. C.
0.25 gram of dibutyl tin dilaurate (T-12) was added and the mixture was
heated to 80.degree. C. and allowed to react for 2 hours.
A premix was made with 325.00 grams of distilled water, 5.28 grams of
triethylamine (TEA), 5.21 grams (0.1734 eq.) of ethylene diamine (EDA) and
5.16 grams (0.0288 eq.) of gamma-aminopropyltrimethoxysilane (A-1110).
170.15 grams (0.2076 eq.) of the prepolymer was added over 10 minutes to
the premix solution in a Microfluidics Homogenizer Model #HC-5000 at an
air line pressure of 0.621 MPa. A stable dispersion was formed. The MEK
was then stripped off under heat and vacuum. The U.B.C. was calculated to
be 1.870.
Example 13
A prepolymer was made in a 1 liter reaction flask equipped with a heating
mantel, condenser, stirring blade, nitrogen inlet and thermometer equipped
with a temperature controller to monitor temperature. 156.27 grams (1.7962
eq.) of toluene diisocyanate (TDI), 157.21 grams (0.1121 eq.) of Arcol
E-351 polyether polyol (an ethylene oxide capped polyoxypropylene diol of
1402.5 av. eq. weight commercially available from Arco Chemical Company),
30.85 grams (0.4598 eq.) of 2,2-bis(hydroxymethyl) propionic acid (DMPA)
and 300 grams of methyl ethyl ketone (MEK) were heated with stirring to
40.degree.-50.degree. C. Next, 0.06g of bis(lauryl,dibutyltin)oxide was
added and the mixture was heated to 80.degree. C. and allowed to react for
2 hours.
The prepolymer was chain extended with 50.00 grams 1,4-butanediol and the
reaction was allowed to run for another 30 minutes. The prepolymer was
then capped with 22.22 grams (0.113 1 eq.) of
.gamma.-mercaptopropyltrimethoxysilane (A-189). The end capping reaction
was catalyzed with 1 gram of Dabco 33LV (triethylene diamine at 33% solids
in dipropylene glycol) for 30 minutes.
173.00 grams (0,2363 eq.) of the polymer was emulsified in 325 grams of
distilled water and 5.28 grams of triethylamine. The polymer was added to
the water-amine solution over 2-4 minutes. The solvent was then removed
from the emulsion with a roto-evaporator. The U.B.C. was calculated to be
1.937.
TABLE 1
__________________________________________________________________________
Ex.
RT 160.degree. F. Stability
Viscosity
H.sub.2 O
MEK Tensile
Elongation
No.
Stability
(days to gel)
pH (cps)
Resistance
Resistance
(psi)
(%)
__________________________________________________________________________
1 Good 18 8.5
20 Good Good 4834 177
C-1
Good 18 8.3
32,000
Poor Poor 447 319
2 Good 7 7.5*
22 Good Good 2466 102
C-2
Poor 18 7.5*
12.5 -- -- 208**
>500
3 Good 28 9.8
18 Good Good 2115 7
C-3
Poor -- 10.1
15 -- -- -- --
4 Good 25 8.0*
22 Good Good 1890 235
C-4
Gelled during emulsification
5 Good 7 7.4*
25 Good Good -- --
C-5
Gelled during emulsification
C-6
Gelled during emulsification
7 Good 18 7.4*
15 Good Good 2820 331
8 Good 11 9.4
15 Good Good 3234 226
9 Good 25 8.9
200 Good Good 2358 211
__________________________________________________________________________
*pH adjusted to approx. 8.5 using 28% NH.sub.4 OH
**Tensile strength at 500% elongation not at failure or break
WOOD COATING EXAMPLES
Example 14
A wood furnishing coating was made in the following manner: A prepolymer
having a lower molecular weight polyester polyol segment was made in a 0.5
liter reaction flask equipped with a heating mantel, condenser, stirring
blade, nitrogen inlet and thermometer. 170.95 grams (1.533 eq.) of
isophorone diisocyanate (IPDI), 121.07 grams (0.291 eq.) of Tone 210.TM.
(a caprolactone-based diol), 19.32 grams (0.288 eq.) of
2,2-bis(hydroxymethyl) propionic acid (DMPA), 10.34 grams (0.229 eq.) of
1,4 butanediol, 6.65 grams (0.147 eq.) of TMP, and 11.14 grams of N-methyl
pyrrolidone (NMP) were heated with stirring to 60.degree.-80.degree. C.
0.04 gram of T-9 (a stannous octanoate catalyst) was added and the mixture
was allowed to heat at 80.degree. C. for an 1 hour. After 80% of the
monomers in this mixture were converted to prepolymer as measured by
standard titrametric procedures with a dibutylamine and HCl indicator
solution, 13.95 grams (0.0367 eq.) of Cythane.TM. 3160 (a trifunctional
polyisocyanate adduct) was then added and the mixture was reacted for
another 45 minutes.
A premix was made with 402.00 grams of deionized water, 7.44 grams of
triethylamine (TEA), 6.40 grams (0.2133 eq.) of ethylene diamine (EDA) and
6.83 grams (0.061 eq.) of Silane Q2-8038 (.gamma.-aminopropylmethyl
dimethoxy silane).
200.00 grams (0.305 eq.) of the prepolymer was emulsified in the premix
solution. The polyurethane dispersion was made into finish by
incorporating the proper levelling, wetting, defoaming, thickening,
surface active, and mar resistant agents and other additives as given
below. This finish was then coated and cured on an oak panel as specified
in the above test methods and tested for solvent resistance, stain
resistance and gloss. The results of these tests may be found in Table 2.
The U.B.C. was calculated to be 1.84.
______________________________________
Polyurethane Dispersion
100.0 grams
Byk .TM. 301.sup.1 0.27 grams
FC-129 (1%).sup.2 0.92 grams
Igepal .TM. CO-630.sup.3
0.22 grams
SWS 211.sup.4 0.55 grams
Acrylsol .TM. TT935.sup.5
0.82 grams
Butyl Carbitol.sup.6 3.5 grams
Propylene Glycol.sup.6
2.5 grams
D.I. Water 2.73 grams
Adjusted pH 8.5 grams
______________________________________
.sup.1 a mar aid and defoaming agent available from Byk Chemie
.sup.2 a fluorochemical surfactant available from 3M Co.
.sup.3 a surfactant commercially available from RhonePoulene
.sup.4 an antifoam emulsion available from Wacker Silicone Corp.
.sup.5 a thickener available from Rohm and Haas
.sup.6 optional coalescing agents
Example 15
A wood furniture coating was. prepared according to the method of Example
14, except without the incorporation of the polyfunctional isocyanate
adduct in the prepolymer. A prepolymer was prepared from 125.00 grams
(1.12 eq.) of IPDI, 134.72 grams (0.2161 eq.) of Tone.TM. 230 (a high
molecular weight polycaprolactone diol), 17.00 grams (0.2537 eq.) of DMPA,
7.20 grams (0.1598 eq.) of 1,4-butanediol, 3.00 grams (0.0672 eq.) of TMP,
0.02 grams of T-9 stannous octanoate catalyst, 4.75 grams of stabilizers
(3.25 grams Tinuvin.TM. 144 and 1.50 grams Irganox.TM. 245), 10.00 grams
of NMP, and 30.00 grams of MEK.
The polyurethane dispersion was prepared by adding 250.00 grams of the
prepolymer to a premix solution containing 508.00 grams of deionized
water, 9.66 grams of triethylamine, 8.10 grams (0.27 eq.) of ethylene
diamine, and 5.40 grams (0.0482 eq.) of Silane Q2-8038
(.gamma.-aminopropylmethyl dimethoxysilane) and then the MEK was stripped
from the dispersion.
The polyurethane dispersion was made into a finish, which was then coated
and cured on an oak panel as specified in the above test methods and
tested for solvent resistance, stain resistance and gloss. The results of
these tests may be found in Table 2.
TABLE 2
______________________________________
Example No. 14 15
______________________________________
Solvent Resistance* 28 19
Stain Resistance** 20 18
Gloss 83.3 83.7
______________________________________
*Maximum score attainable 28
**Maximum score attainable 22
Examples 14 and 15 demonstrate the improved solvent and stain resistance in
these wood furniture coating formulations resulting from the addition of
the polyfunctional isocyanate adduct to the polyurethane prepolymer. These
wood furniture finishes also exhibit excellent stain resistance and gloss
comparable to or exceeding those properties of polyurethane products which
are currently commercially available.
Wood Floor Coatings
Example 16
A polyurethane coating employing a mixture of polyether and polyester
polyols which is useful as a wood floor finish was made according to the
method of Example 14. A prepolymer was prepared from a mixture of
polyester and polyether polyols from 131.06 .grams (1.175 eq.) of IPDI,
39.40 grams (0.0394 eq.) of Terethane.TM.-2000 (a poly(tetramethylene
ether glycol)), 119.84 grams (0.1923) of Tone.TM. 230 (a
caprolactone-based polyol), 17.57 grams (0.2622 eq.) of DMPA, 2.54 grams
(0.5638 eq.) of 1,4-butanediol, 3.33 grams (0.0746 eq.) of TMP. After 80%
of the monomers in this mixture were converted to prepolymer as measured
by standard titrametric procedures with a dibutylamine and HCl indicator
solution, 15.71 grams (0.0413 eq.) of Cythane.TM. 3160 (a trifunctional
polyisocyanate adduct), 16.00 grams of NMP, 28.0 grams of MEK, 0.04 gram
of T-9, and 3.0 grams of stabilizers (2.00 grams Tinuvin.TM. 292 and 1.00
gram Irganox.TM. 245).
The dispersion was prepared by adding 150.00 grams (132.45 grams solids) of
the above prepolymer into a premix solution containing 305.00 grams of
deionized water, 5.00 grams of triethylamine, 5.50 grams (0.1833 eq.) of
EDA, and 5.40 grams (0.0482 eq.) of Silane Q2-8038, followed by the
stripping of the MEK.
The polyurethane dispersion was made into a wood floor finish, which was
then coated and cured on an oak panel as specified in the above test
methods and tested for solvent resistance, abrasion resistance, impact
resistance and adhesion to a wood flooring sample. The results of these
tests may be found in Table 3. The U.B.C. was calculated to be 1.999.
Example 17
A polyurethane wood floor finish was prepared in accordance with Example
16, except that a higher amount of isocyanate-reactive silane compound was
incorporated in the premix; i.e., 5.93 grams (0.0529 eq.) of Silane
Q2-8038 (.gamma.-aminopropylmethyl dimethoxysilane).
The polyurethane wood floor finish was then coated and cured on an oak
panel as specified in the above test methods and tested for solvent
resistance, abrasion resistance, impact resistance and adhesion to a wood
flooring sample. The results of these tests may be found in Table 3. The
U.B.C. was calculated to be 2.014.
Example 18
A polyurethane coating employing a polyester polyol which is useful as a
wood floor finish was made according to the method of Example 14. A
prepolymer was prepared from 152.33 grams (1.3482 eq.) of IPDI, 150.68
grams (0.3197 eq.) of LEX1400-120 (a linear poly(1,6-hexanediol-neopentyl
glycol-adipate)), 16.38 grams (0.2444 eq.) of DMPA, 4.06 grams (0.090 eq.)
of 1,4-butanediol, 6.55 grams (0.1467 eq.) of TMP. After 80% of the
monomers in this mixture were converted to prepolymer as measured by
standard titrametric procedures with a dibutylamine and HCl indicator
solution, 14.75 grams (0.0388 eq.) of Cythane.TM. 3160 (a trifunctional
polyisocyanate adduct), 0.04 gram of T-9 catalyst, 16.00 grams of NMP,
28.00 grams of MEK, and 4.00 grams of stabilizers (2.00 grams Tinuvin.TM.
292 and 2.00 grams Irganox.TM. 1010).
The dispersion was prepared by adding 150.00 grams (133.20 grams solids) of
prepolymer to a premix solution containing 305.00 grams of deionized
water, 5.03 grams of triethylamine, 5.40 (0.18 eq.) of EDA and 5.40 grams
(0.0482 eq.) of Silane Q2-8038 (.gamma.-aminopropylmethyl
dimethoxysilane), and the MEK was removed.
The polyurethane dispersion was made into a wood floor finish, which was
then coated and cured on an oak panel as specified in the above test
methods and tested for solvent resistance, abrasion resistance, impact
resistance and adhesion to a wood flooring sample. The results of these
tests may be found in Table 3.
Example 19
A polyurethane coating employing a mixture of polyether polyols which is
useful as a wood floor finish was made according to the method of Example
14. A prepolymer was prepared from 103.55 grams (0.9287 eq.) of IPDI,
150.19 grams (0.1502 eq.) of ARCOL.TM. 2025 (a poly(propylene glycol)),
28.37 grams (0.0279 eq.) of Terethane.TM.-2000 (a poly(tetramethylene
ether glycol)), 2.27 grams (0.05039 eq.) of 1,4-butanediol, 15.60 grams
(0.2328 eq.) of DMPA, 18.00 grams of NMP, 0.04 gram of T-9 catalyst, and
total 6.00 grams of stabilizers (2.00 grams Tinuvin.TM. 292, 2.00 grams
Tinuvin.TM. 328, and 2.00 grams Irganox.TM. 1010).
The dispersion from this prepolymer was made by adding 125.00 grams (118.00
grams solids) of prepolymer into a premix containing a solution of 250.00
grams of deionized water, 4.49 grams of triethylamine, 4.51 grams (0.1503
eq.) EDA and 3.13 grams (0.0279 eq.) of Silane Q2-8038
(.gamma.-aminopropylmethyl dimethoxysilane), and the MEK was removed.
The polyurethane dispersion was made into a wood floor finish, which was
then coated and cured on an oak panel as specified in the above test
methods and tested for solvent resistance, abrasion resistance, impact
resistance and adhesion to a wood flooring sample. The results of these
tests may be found in Table 3.
Example 20
A polyurethane wood floor finish was prepared in accordance with Example
19, except that a higher amount of isocyanate-reactive silane compound was
incorporated in the premix; i.e., 4.88 grams (0.0435 eq.) of Silane
Q2-8038 (.gamma.-aminopropylmethyl dimethoxysilane).
The polyurethane wood floor finish was then coated and cured on an oak
panel as specified in the above test methods and tested for solvent
resistance, abrasion resistance. impact resistance and adhesion to a wood
flooring sample. The results of these tests may be found in Table 3.
Example 21
A polyurethane coating employing a crystallizable polyester polyol which is
useful as a wood floor finish was made according to the method of Example
14. A prepolymer was prepared from 63.00 grams (0.5650 eq.) of IPDI,
130.00 grams (0.06952 eq.) of LEX1130-30 (a linear poly(1,6-hexanediol
adipate)), 11.00 grams (0.1642 eq.) of DMPA, 1.3 grams (0.0288 eq.) of
1,4-butanediol, 0.50 grams (0.1119 eq.) of TMP, 0.04 gram of T-9 catalyst,
10.00 grams of NMP, 40.00 grams of MEK, and total stabilizers of 5.08
grams of stabilizers (2.14 grams Tinuvin.TM. 292, 2.27 grams Tinuvin.TM.
328, and 0.67 gram Irganox.TM. 1010).
The dispersion was made from this prepolymer by adding 150.00 grams (121.20
grams solids) of the prepolymer into a premix solution containing 300.00
grams of deionized water, 4.72 grams of triethylamine, 3.89 grams (0.1297
eq.) of EDA, and 4.50 (grams 0.0402 eq.) of Silane Q2-8038
(.gamma.-aminopropylmethyl dimethoxysilane), and MEK was removed.
The polyurethane dispersion was made into a wood floor finish which was
then coated and cured on an oak panel as specified in the above test
methods and tested for solvent resistance, abrasion resistance, impact
resistance and adhesion to a wood flooring sample. The results of these
tests may be found in Table 3.
Example 22
A polyurethane coating employing a mixture of crystallizable polyester
polyols which is useful as a wood floor finish was made according to the
method of Example 14. A prepolymer was prepared from 32.00 grams (0.2869
eq.) of IPDI, 49.00 grams (0.0262 eq.) of LEX1130-30 (a higher molecular
weight linear poly(1,6-hexanediol adipate)), 12.7 grams (0.1245 eq.) of
LEX1130-55 (a lower molecular weight linear poly(1,6-hexanediol adipate)),
5.34 grams (0.0797 eq.) of DMPA, 0.25 grams (0.0559 eq.) of TMP, 0.04 gram
of T-9 catalyst, 3.00 grams of NMP, and 12.0 grams of MEK.
the dispersion was prepared by adding 100.00 grams (86.96 grams solids) of
the prepolymer into a premix solution containing 200.00 grams deionized
water, 3.39 grams triethylamine, 2.54 grams (0.0849 eq.) of EDA, 3.9 grams
(0.0348 eq.) of Silane Q2-8038 (.gamma.-aminopropylmethyl
dimethoxysilane), and then the MEK was removed.
The polyurethane dispersion was made into a wood floor finish which was
then coated and cured on an oak panel as specified in the above test
methods and tested for solvent resistance, abrasion resistance, impact
resistance and adhesion to a wood flooring sample. The results of these
tests may be found in Table 3.
Example 23
A polyurethane coating employing a mixture of crystallizable polyester
polyols which is useful as a wood floor finish was made according to the
method of Example 14. A prepolymer was prepared from 35.55 grams (0.3188
eq.) of IPDI, 48.89 grams (0.03055 eq.) of LEX1400-35 (a higher molecular
weight poly(1,6-hexanediol adipate)), 8.89 grams (0.0189 eq.) of LEX
1400-120 (a higher molecular weight poly(1,6-hexanediol adipate)), 4.89
grams (0.0730 eq.) of DMPA, 1.78 grams (0.0399 eq.) of TMP, 0.04 gram of
T-9 catalyst, 5.00 grams of NMP, and 20.00 grams of MEK.
The dispersion was prepared by adding 100.00 grams of prepolymer into a
premix solution containing 200.00 grams of deionized water, 3.01 grams of
triethylamine, 3.00 grams (0.10 eq.) of EDA, and 3.00 grams of silane
Q2-8038 (.gamma.-aminopropylmethyl dimethoxysilane), and the MEK was
removed.
The polyurethane dispersion was made into a wood floor finish which was
then coated and cured on an oak panel as specified in the above test
methods and tested for solvent resistance, abrasion resistance, impact
resistance and adhesion to a wood flooring sample. The results of these
tests may be found in Table 3.
TABLE 3
__________________________________________________________________________
Abrasion
Resistance
Abrasion Resistance
(grams lost)
(grams lost) Impact
H-22, 50 cycles,
CS-17, 1000 cycles,
Solvent
Resistance,
Ex.
500 grams
1000 grams
Resistance
(cm) Adhesion
__________________________________________________________________________
16 6.5 27.3 28 20 5B
17 18.3 28 >80 5B
18 7.2 28 5B
19 19.8 28 >80 5B
20 14.5 28 >80 5B
21 4.5 22 >80 5B
22 6.4 26 >80 5B
23 18.8 28 >80 5B
C4 11.3 29.2 28
C5 16.2
C6 13.7 32.5 28
__________________________________________________________________________
C4 is Street Shoe, a two part crosslinked waterborne polyurethane floor
coating available from Basic Coatings Co.
C5 is Pacific Strong, a one part crosslinked waterborne polyurethane floo
coating available from Bona Kemi USA Inc.
C6 is Ultracure Cure, a two part crosslinked waterborne polyurethane floo
coating available from Bona Kemi USA Inc.
Table 3 illustrates several significant aspects in formulating wood
finishes from the polyurethane dispersions of the present invention. The
effect of level of isocyanate reactive silane on the durability of these
coatings is demonstrated by the superior abrasion resistance of Examples
17 and 20, which contain greater than 3.5 grams of silane/100 grams
prepolymer, when compared respectively to Examples 16 and 19 which have a
lower isocyanate reactive silane content. Furthermore, Table 3 indicates
the effect of polyol molecular weight on the durability (i.e., abrasion
resistance), solvent resistance and impact resistance of the polyurethane
coatings of the present invention. In general, polyurethane coatings
containing lighter molecular weight polyols, such as Examples 21 and 22,
exhibit higher durability and flexibility than similar compositions
comprising lower molecular weight polyol segments, such as the
compositions of Examples 16-20 and 23. This enhanced toughness, however,
comes at the expense of reduced solvent resistance.
Example 24
A marine wood coating was prepared based on the silyl-terminated urethane
dispersions of the present invention as follows: A prepolymer was made in
a 1 liter reaction flask equipped with a heating mantel, condenser,
stirring blade, nitrogen inlet and thermometer equipped with a temperature
controller to monitor temperature. 308.23 grams (2.3351 eq.) of
4,4'-cyclohexylmethane diisocyanate (DES W), 360.72 grams (0.5787 eq.) of
Tone.TM. 230 (a caprolactone-based polyol), 40.10 grams (0.5976 eq.) of
2,2-bis(hydroxymethyl) propionic acid (DMPA) and 125.10 grams of n-methyl
pyrrolidone (NMP) were heated with stirring to 40.degree.-50.degree. C.
0.081 gram of dibutyl tin dilaurate (T-12) was added and the mixture was
heated to 80.degree. C. and allowed to react for 2 hours.
A premix was made with 325.00 grams of distilled water, 5.28 grams of
triethylamine (TEA), 6.00 grams (0.1997 eq.) of ethylene diamine (EDA) and
6.00 grams (0.0335 eq.) of gamma-aminopropyltrimethoxysilane (A-1110).
170.15 grams (0.2363 eq.) of the prepolymer was added over 10 minutes to
the premix solution in a Microfluidics Homogenizer Model #HC-5000 at an
air line pressure of 0.621 MPa. The polyurethane dispersion was made into
a coating by blending the proper wetting and light stabilizing agents and
other additives as given below with the polyurethane dispersion in a low
shear air mixer for 10 minutes. Addition of 0.01 and 0.05 g of a
thickening agent to separate dispersions, followed by mixing for 10
minutes, resulted in wood coatings having viscosities of 375 and 6000 cps,
respectively.
______________________________________
Polyurethane Dispersion
100.0 grams
Mackamine .TM. CO.sup.1
2.0 grams
Tergitol .TM. TMN-3.sup.2
1.0 gram
Tinuvin .TM. 292.sup.3
1.0 gram
Tinuvin .TM. 1130.sup.4
1.0 gram
Alcogum .TM..sup.5 0.01 gram
______________________________________
.sup.1 an alkyl amine oxide wetting agent available from McIntyre Group,
Ltd.
.sup.2 a 2,6,8trimethyl-4-nonyl oxypolyethylene oxyethanol wetting agent
available from Union Carbide Co.
.sup.3 a hindered amine photostabilizer commercially available from
CibaGeigy Ltd.
.sup.4 a phenolic based antioxidant commercially available from CibaGeigy
Ltd.
.sup.5 a sodium polyacrylate associative thickener available from Alco
Chemical Corp.
This finish was then coated and cured on a teak wood panel as specified in
the above test method and tested for weathering resistance. The results of
these tests may be found in Table 4, along with weathering resistance test
data for solventborne commercially available coating formulations and the
unmodified silyl-terminated polyurethane dispersion composition of Example
1.
TABLE 4
__________________________________________________________________________
Example
250 hours
500 hours
1000 hours
2000 hours
3000 hours
__________________________________________________________________________
24 No change
No change
No change
No change
No change
1 No change
Loss of
Coating
As at 1000
50% of
surface
yellowing
hours, coating
gloss and flaking
flaking worse
gone
C-7.sup.1
No change
No change
Losing gloss,
No change
As at 2000
coating dull
to 1000 hours
hours, but worse
C-8.sup.2
No change
No change
Losing No change
Loss of
gloss, to 1000
gloss,
coating dull
hours yellowing
C-9.sup.3
No change
No change
Losing No change
Loss of
gloss, to 1000
gloss,
coating dull
hours yellowing
__________________________________________________________________________
.sup.1 Epifanes .TM., manufactured by W. Heeren en Zoon, B.V., a
solventborne one part alkyd resin marine varnish;
.sup.2 Dolphinite .TM. 1600, manufactured by KopCoat Inc., a solventborne
one part alkyd resin marine varnish;
.sup.3 Interlux .TM. #95, manufactured by Cortaulds Coatings, Ltd., a
solventborne one part alkyd resin marine varnish.
Table 4 illustrates the superior weathering performance of the marine
coatings of the present invention, particularly when formulated with
proper light stabilizing, wetting and thickening agents. The dispersion of
Example 24 also demonstrates that weathering resistance of the
silyl-terminated polyurethane dispersion meets or exceeds the
weatherability of traditional, less desirable solvent based coating
compositions.
Various modifications and alterations of this invention will become
apparent to those skilled in the art without departing from the scope and
spirit of this invention, and it should be understood that this invention
is not to be unduly limited to the illustrative embodiments set forth
herein.
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